View Filing Data

Document and Entity Information - shares	3 Months Ended
Document and Entity Information - shares	Mar. 31, 2013	Apr. 29, 2013
Document and Entity Information
Entity Registrant Name	TC PIPELINES LP
Entity Central Index Key	0001075607
Document Type	10-Q
Document Period End Date	Mar. 31, 2013
Amendment Flag	false
Current Fiscal Year End Date	--12-31
Entity Current Reporting Status	Yes
Entity Filer Category	Large Accelerated Filer
Entity Common Stock, Shares Outstanding		53,472,766
Document Fiscal Year Focus	2013
Document Fiscal Period Focus	Q1

CONSOLIDATED STATEMENT OF INCOME shares in Millions, $ in Millions	3 Months Ended
	Mar. 31, 2013 USD ($) $ / shares shares	Mar. 31, 2012 USD ($) $ / shares shares
CONSOLIDATED STATEMENT OF INCOME
Equity earnings from unconsolidated affiliates (Note 4)	$ 26	$ 38
Transmission revenues	17	16
Operating expenses	(4)	(4)
General and administrative	(2)	(2)
Depreciation	(3)	(3)
Financial charges and other	(5)	(6)
Net income	29	39
Net income allocation (Note 6)
Common units	28	38
General Partner	1	1
Net income allocated to partners	$ 29	$ 39
Net income per common unit (Note 6) - basic (in dollars per unit) \| $ / shares	0.52	0.71
Net income per common unit (Note 6) - diluted (in dollars per unit) \| $ / shares	0.52	0.71
Weighted average common units outstanding (millions) - basic (in units) \| shares	53.5	53.5
Weighted average common units outstanding (millions) - diluted (in units) \| shares	53.5	53.5
Common units outstanding, end of period (millions) (in units) \| shares	53.5	53.5

CONSOLIDATED STATEMENT OF COMPREHENSIVE INCOME - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
CONSOLIDATED STATEMENT OF COMPREHENSIVE INCOME
Net income	$ 29	$ 39
Other comprehensive income
Total comprehensive income	$ 29	$ 39

- Definition

The change in equity [net assets] of a business enterprise during a period from transactions and other events and circumstances from non-owner sources which are attributable to the reporting entity. It includes all changes in equity during a period except those resulting from investments by owners and distributions to owners, but excludes any and all transactions which are directly or indirectly attributable to that ownership interest in subsidiary equity which is not attributable to the parent.

+ References + Details

- Definition

The portion of profit or loss for the period, net of income taxes, which is attributable to the parent.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Glossary Net Income
-URI http://asc.fasb.org/extlink&oid=6518256

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 28
-URI http://asc.fasb.org/extlink&oid=6943989&loc=d3e3602-108585

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-Name Accounting Standards Codification
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-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-04.19)
-URI http://asc.fasb.org/extlink&oid=6879464&loc=d3e573970-122913

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-URI http://asc.fasb.org/extlink&oid=6880815&loc=d3e20235-122688

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Reference 7: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
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-Name Accounting Standards Codification
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-Publisher AICPA
-Name Accounting Research Bulletin (ARB)
-Number 51
-Paragraph 38
-Subparagraph d
-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 10: http://www.xbrl.org/2003/role/presentationRef
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Reference 11: http://www.xbrl.org/2003/role/presentationRef
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-Name Accounting Research Bulletin (ARB)
-Number 51
-Paragraph A7
-Appendix A

Reference 12: http://www.xbrl.org/2003/role/presentationRef
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-Name Emerging Issues Task Force (EITF)
-Number 87-21
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Reference 13: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Section 03
-Paragraph 19
-Article 5

Reference 14: http://www.xbrl.org/2003/role/presentationRef
-Publisher AICPA
-Name Accounting Research Bulletin (ARB)
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-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 15: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 95
-Paragraph 28, 29, 30
-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 16: http://www.xbrl.org/2003/role/presentationRef
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-Number 210
-Section 04
-Paragraph 20
-Article 9

+ Details

CONSOLIDATED BALANCE SHEET - USD ($) $ in Millions	Mar. 31, 2013	Dec. 31, 2012
Current Assets
Cash and cash equivalents	$ 2	$ 3
Accounts receivable and other (Note 11)	8	9
Total current assets	10	12
Investments in unconsolidated affiliates (Note 4)	1,556	1,563
Plant, property and equipment (Net of $153 accumulated depreciation; 2012-$150)	283	288
Goodwill	130	130
Other assets	5	5
Total assets	1,984	1,998
Current Liabilities
Accounts payable and accrued liabilities	5	7
Accrued interest	5	1
Current portion of long-term debt (Note 5)	3	3
Total current liabilities	13	11
Long-term debt (Note 5)	682	685
Other liabilities	2	1
Total liabilities	697	697
Partners' Equity
Common units	1,261	1,275
General partner	27	27
Accumulated other comprehensive loss	(1)	(1)
Total partners' equity	1,287	1,301
Total liabilities and partners' equity	$ 1,984	$ 1,998

CONSOLIDATED BALANCE SHEET (Parenthetical) - USD ($) $ in Millions	Mar. 31, 2013	Dec. 31, 2012
CONSOLIDATED BALANCE SHEET
Plant, property and equipment, accumulated depreciation	$ 153	$ 150

- Definition

The cumulative amount of depreciation, depletion and amortization (related to property, plant and equipment, but not including land) that has been recognized in the income statement.

+ References + Details

CONSOLIDATED STATEMENT OF CASH FLOWS - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Cash Generated From Operations
Net income	$ 29	$ 39
Depreciation	3	3
Increase in long-term liabilities	1
Decrease in operating working capital (Note 8)	3	7
Total cash generated from operations	36	49
Investing Activities
Proceeds from settlement recoveries	2
Total investing activities	9	4
Financing Activities
Distributions paid (Note 7)	(43)	(42)
Long-term debt issued (Note 5)	2
Long-term debt repaid (Note 5)	(5)	(35)
Total financing activities	(46)	(77)
Decrease in cash and cash equivalents	(1)	(24)
Cash and cash equivalents, beginning of period	3	29
Cash and cash equivalents, end of period	2	5
Great Lakes
Investing Activities
Cumulative distributions in excess of equity earnings:	4	2
Investment in Great Lakes (Note 4)	(4)	(4)
Northern Border
Investing Activities
Cumulative distributions in excess of equity earnings:	5	5
GTN
Investing Activities
Cumulative distributions in excess of equity earnings:	1
Bison
Investing Activities
Cumulative distributions in excess of equity earnings:	$ 1	$ 1

CONSOLIDATED STATEMENT OF CHANGES IN PARTNERS' EQUITY - 3 months ended Mar. 31, 2013 - USD ($) shares in Millions, $ in Millions	Total	Common Units	General Partner	Accumulated Other Comprehensive Loss
Partners' equity at Dec. 31, 2012	$ 1,301	$ 1,275	$ 27	$ (1)
Partners' equity (in units) at Dec. 31, 2012	53.5	53.5
Increase (Decrease) in Partners' Equity
Net income	$ 29	$ 28	1
Distributions paid	(43)	(42)	(1)
Partners' equity at Mar. 31, 2013	$ 1,287	$ 1,261	$ 27	$ (1)
Partners' equity (in units) at Mar. 31, 2013	53.5	53.5

- Definition

The portion of profit or loss for the period, net of income taxes, which is attributable to the parent.

+ References

+ Details

- Definition

The amount of ownership interest of different classes of partners in limited partnership.

+ References + Details

- Definition

The number of each class of partnership units outstanding at the balance sheet date. Units represent shares of ownership of the general, limited, and preferred partners.

+ References + Details

ORGANIZATION	3 Months Ended
ORGANIZATION	Mar. 31, 2013
ORGANIZATION
ORGANIZATION	NOTE 1 ORGANIZATION TC PipeLines, LP and its subsidiaries are collectively referred to herein as the Partnership. The Partnership was formed by TransCanada PipeLines Limited, a wholly-owned subsidiary of TransCanada Corporation (TransCanada Corporation together with its subsidiaries collectively referred to herein as TransCanada), to acquire, own and participate in the management of energy infrastructure assets in North America.

SIGNIFICANT ACCOUNTING POLICIES	3 Months Ended
SIGNIFICANT ACCOUNTING POLICIES	Mar. 31, 2013
SIGNIFICANT ACCOUNTING POLICIES
SIGNIFICANT ACCOUNTING POLICIES	NOTE 2 SIGNIFICANT ACCOUNTING POLICIES The accompanying financial statements and related notes have been prepared in accordance with United States generally accepted accounting principles (GAAP) and amounts are stated in U.S. dollars. The results of operations for the three months ended March 31, 2013 and 2012 are not necessarily indicative of the results that may be expected for a full fiscal year. The accompanying financial statements should be read in conjunction with the financial statements and notes thereto included in our Annual Report on Form 10-K for the year ended December 31, 2012. That report contains a more comprehensive summary of the Partnership’s major accounting policies. In the opinion of management, the accompanying financial statements contain all of the appropriate adjustments, all of which are normally recurring adjustments unless otherwise noted, considered necessary to present fairly the financial position of the Partnership, the results of operation and cash flows for the respective periods. Our significant accounting policies are consistent with those disclosed in Note 2 of the financial statements in our Annual Report on Form 10-K for the year ended December 31, 2012. Certain items from that Note are repeated or updated below as necessary to assist in understanding the accompanying financial statements. (a) Basis of Presentation The Partnership uses the equity method of accounting for its investments in Great Lakes, Northern Border, GTN and Bison, over which it is able to exercise significant influence. The Partnership consolidates its investments in North Baja and Tuscarora. (b) Use of Estimates The preparation of financial statements requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities as of the date of the financial statements, and the reported amounts of revenues and expenses during the reporting period. Although management believes these estimates are reasonable, actual results could differ from these estimates.

ACCOUNTING PRONOUNCEMENTS	3 Months Ended
ACCOUNTING PRONOUNCEMENTS	Mar. 31, 2013
ACCOUNTING PRONOUNCEMENTS
ACCOUNTING PRONOUNCEMENTS	NOTE 3 ACCOUNTING PRONOUNCEMENTS Future Accounting Changes Obligations Resulting from Joint and Several Liability Arrangements In February 2013, the Financial Accounting Standards Board (FASB) issued guidance for the recognition, measurement, and disclosure of obligations resulting from joint and several liability arrangements for which the total amount of the obligation is fixed at the reporting date. Examples of obligations within the scope of this Accounting Standards Update (ASU) include debt arrangements, other contractual obligations, and settled litigation and judicial rulings. This ASU is effective retrospectively for fiscal years, and interim periods within those years, beginning after December 15, 2013. The Partnership is currently evaluating the impact of the adoption of this ASU on its consolidated financial statements, but does not expect it to have a material impact.

- Definition

The entire disclosure of changes in accounting principles, including adoption of new accounting pronouncements, that describes the new methods, amount and effects on financial statement line items.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Glossary Direct Effects of a Change in Accounting Principle
-URI http://asc.fasb.org/extlink&oid=6510796

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Glossary Change in Accounting Principle
-URI http://asc.fasb.org/extlink&oid=6507316

Reference 3: http://www.xbrl.org/2003/role/presentationRef
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-Name Accounting Standards Codification
-Topic 250
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Reference 4: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Glossary Indirect Effects of a Change in Accounting Principle
-URI http://asc.fasb.org/extlink&oid=6515603

Reference 5: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 270
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.10-01.(b)(6))
-URI http://asc.fasb.org/extlink&oid=6958853&loc=d3e46468-122699

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-Name Accounting Standards Codification
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-URI http://asc.fasb.org/extlink&oid=6503790

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-Name Accounting Standards Codification
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-URI http://asc.fasb.org/extlink&oid=6523989

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-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Section 01
-Paragraph b
-Subparagraph 6
-Article 10

+ Details

INVESTMENTS IN UNCONSOLIDATED AFFILIATES

3 Months Ended

Mar. 31, 2013

INVESTMENTS IN UNCONSOLIDATED AFFILIATES

INVESTMENTS IN UNCONSOLIDATED AFFILIATES

NOTE 4 INVESTMENTS IN UNCONSOLIDATED AFFILIATES

Great Lakes, Northern Border, GTN and Bison are regulated by FERC and are operated by TransCanada. The Partnership uses the equity method of accounting for its interests in its equity investees.

	Ownership	Equity Earnings from Unconsolidated Affiliates		Investments in Unconsolidated Affiliates
	Interest at	Three months
(unaudited)	March 31,	ended March 31,		March 31,	December 31,
(millions of dollars)	2013	2013	2012	2013	2012

Great Lakes	46.45%	2	9	677	677
Northern Border (a)	50%	16	20	507	512
GTN	25%	5	6	215	216
Bison	25%	3	3	157	158
		26	38	1,556	1,563

(a) Equity earnings from Northern Border is net of the 12-year amortization of a $10 million transaction fee paid to the operator of Northern Border at the time of the Partnership’s additional 20 percent interest acquisition in April 2006.

Great Lakes

The Partnership made an equity contribution to Great Lakes of $4 million in the first quarter of 2013. This amount represents the Partnership’s 46.45 percent share of a $9 million cash call from Great Lakes to make a scheduled debt repayment.

The Partnership recorded no undistributed earnings from Great Lakes for the three months ended March 31, 2013 and 2012.

The summarized financial information for Great Lakes is as follows:

(unaudited)
(millions of dollars)	March 31, 2013	December 31, 2012

ASSETS
Current assets	51	56
Plant, property and equipment, net	792	799
	843	855

Liabilities and Partners’ Equity
Current liabilities	27	30
Long-term debt, including current maturities	345	354
Partners’ equity	471	471
	843	855

	Three months ended
(unaudited)	March 31,
(millions of dollars)	2013		2012

Transmission revenues	35		49
Operating expenses	(15	)	(15	)
Depreciation	(8	)	(8	)
Financial charges and other	(7	)	(7	)
Net income	5		19

Northern Border

In January 2013, FERC gave final approval for the Northern Border Settlement which establishes maximum transportation rates and charges on the Northern Border system effective January 1, 2013. Northern Border’s previous reservation rates were reduced by approximately 11 percent as a result of this settlement.

The Partnership recorded no undistributed earnings from Northern Border for the three months ended March 31, 2013 and 2012.

The summarized financial information for Northern Border is as follows:

(unaudited)
(millions of dollars)	March 31, 2013	December 31, 2012

ASSETS
Cash and cash equivalents	34	28
Other current assets	34	35
Plant, property and equipment, net	1,220	1,234
Other assets	31	31
	1,319	1,328

Liabilities and Partners’ Equity
Current liabilities	53	53
Deferred credits and other	17	16
Long-term debt, including current maturities	473	473
Partners’ equity
Partners’ capital	779	789
Accumulated other comprehensive loss	(3)	(3)
	1,319	1,328

	Three months ended
(unaudited)	March 31,
(millions of dollars)	2013		2012

Transmission revenues	72		81
Operating expenses	(19	)	(18	)
Depreciation	(15	)	(16	)
Financial charges and other	(5	)	(6	)
Net income	33		41

GTN

The Partnership recorded no undistributed earnings from GTN for the three months ended March 31, 2013 and 2012.

The summarized financial information for GTN is as follows:

(unaudited)
(millions of dollars)	March 31, 2013	December 31, 2012

ASSETS
Current assets	62	50
Plant, property and equipment, net	1,162	1,174
Other assets	1	1
	1,225	1,225

Liabilities and Members’ Equity
Current liabilities	17	16
Deferred credits and other	21	20
Long-term debt, including current maturities	325	325
Members’ capital	862	864
	1,225	1,225

	Three months ended
(unaudited)	March 31,
(millions of dollars)	2013		2012

Transmission revenues	49		52
Operating expenses	(11	)	(11	)
Depreciation	(13	)	(13	)
Financial charges and other	(4	)	(5	)
Net income	21		23

Bison

The Partnership recorded no undistributed earnings from Bison for the three months ended March 31, 2013 and 2012.

The summarized financial information for Bison is as follows:

(unaudited)
(millions of dollars)	March 31, 2013	December 31, 2012

ASSETS
Current assets	7	7
Plant, property and equipment, net	645	649
	652	656

Liabilities and Members’ Equity
Current liabilities	25	25
Members’ capital	627	631
	652	656

	Three months ended
(unaudited)	March 31,
(millions of dollars)	2013		2012

Transmission revenues	20		20
Operating expenses	(4	)	(3	)
Depreciation	(5	)	(5	)
Net income	11		12

- Definition

The entire disclosure for equity method investments and joint ventures. Equity method investments are investments that give the investor the ability to exercise significant influence over the operating and financial policies of an investee. Joint ventures are entities owned and operated by a small group of businesses as a separate and specific business or project for the mutual benefit of the members of the group.

+ References + Details

CREDIT FACILITIES AND LONG-TERM DEBT

3 Months Ended

Mar. 31, 2013

CREDIT FACILITIES AND LONG-TERM DEBT

CREDIT FACILITIES AND LONG-TERM DEBT

NOTE 5 CREDIT FACILITIES AND LONG-TERM DEBT

(unaudited)
(millions of dollars)	March 31, 2013	December 31, 2012

Senior Credit Facility due 2017	309	312
4.65% Senior Notes due 2021	349	349
3.82% Series D Senior Notes due 2017	27	27
	685	688
Less: current portion of long-term debt	3	3
	682	685

The Partnership’s Senior Credit Facility consists of a $500 million senior revolving credit facility with a banking syndicate, maturing November 20, 2017, under which $309 million was outstanding at March 31, 2013 (December 31, 2012 - $312 million), leaving $191 million available for future borrowing.

The London Interbank Offered Rate (LIBOR) based interest rate on the Senior Credit Facility averaged 1.46 percent for the three months ended March 31, 2013 (2012 – 1.65 percent). The LIBOR-based interest rate was 1.46 percent at March 31, 2013 (2012 – 1.63 percent).

At March 31, 2013, the Partnership was in compliance with its financial covenants, in addition to the other covenants which include restrictions on entering into mergers, consolidations and sales of assets, granting liens, material amendments to the Second Amended and Restated Agreement of Limited Partnership (Partnership Agreement), incurring additional debt and distributions to unitholders.

Series D Senior Notes are secured by Tuscarora’s transportation contracts, supporting agreements and substantially all of Tuscarora’s property. The note purchase agreement contains certain provisions that include, among other items, limitations on additional indebtedness and distributions to partners.

The principal repayments required on the long-term debt are as follows:

(unaudited)
(millions of dollars)

2013		3
2014		4
2015		4
2016		4
2017		321
Thereafter		349
		685

- Definition

The entire disclosure for information about short-term and long-term debt arrangements, which includes amounts of borrowings under each line of credit, note payable, commercial paper issue, bonds indenture, debenture issue, own-share lending arrangements and any other contractual agreement to repay funds, and about the underlying arrangements, rationale for a classification as long-term, including repayment terms, interest rates, collateral provided, restrictions on use of assets and activities, whether or not in compliance with debt covenants, and other matters important to users of the financial statements, such as the effects of refinancing and noncompliance with debt covenants.

+ References + Details

NET INCOME PER COMMON UNIT

3 Months Ended

Mar. 31, 2013

NET INCOME PER COMMON UNIT

NET INCOME PER COMMON UNIT

NOTE 6 NET INCOME PER COMMON UNIT

Net income per common unit is computed by dividing net income, after deduction of TC PipeLines, GP Inc.’s (General Partner) allocation, by the weighted average number of common units outstanding. The General Partner’s allocation is equal to an amount based upon the General Partner’s effective two percent general partner interest, plus an amount equal to incentive distributions. Incentive distributions are paid to the General Partner if quarterly cash distributions on the common units exceed levels specified in the Partnership Agreement.

Net income per common unit was determined as follows:

	Three months ended
(unaudited)	March 31,
(millions of dollars, except per unit)	2013		2012

Net income	29		39
Net income allocated to General Partner	(1	)	(1	)
Net income allocable to common units	28		38
Weighted average common units outstanding (millions) – basic and diluted	53.5		53.5
Net income per common unit – basic and diluted	$0.52		$0.71

CASH DISTRIBUTIONS	3 Months Ended
CASH DISTRIBUTIONS	Mar. 31, 2013
CASH DISTRIBUTIONS
CASH DISTRIBUTIONS	NOTE 7 CASH DISTRIBUTIONS For the three months ended March 31, 2013, the Partnership distributed $0.78 per common unit (2012 – $0.77 per common unit) for a total of $43 million (2012 - $42 million). The distributions paid for the three months ended March 31, 2013 and 2012 included no incentive distributions to the General Partner.

CHANGE IN WORKING CAPITAL

3 Months Ended

Mar. 31, 2013

CHANGE IN WORKING CAPITAL

CHANGE IN WORKING CAPITAL

NOTE 8 CHANGE IN WORKING CAPITAL

(unaudited)	Three months ended March 31,
(millions of dollars)	2013		2012

Decrease in accounts receivable and other	1		1
Increase/(decrease) in accounts payable and accrued liabilities	(2	)	1
Increase in accrued interest	4		5
Decrease in operating working capital	3		7

RELATED PARTY TRANSACTIONS

3 Months Ended

Mar. 31, 2013

RELATED PARTY TRANSACTIONS

RELATED PARTY TRANSACTIONS

NOTE 9 RELATED PARTY TRANSACTIONS

The Partnership does not have any employees. The management and operating functions are provided by the General Partner. The General Partner does not receive a management fee in connection with its management of the Partnership. The Partnership reimburses the General Partner for all costs of services provided, including the costs of employee, officer and director compensation and benefits, and all other expenses necessary or appropriate to the conduct of the business of, and allocable to, the Partnership. Such costs include (i) overhead costs (such as office space and equipment) and (ii) out-of-pocket expenses related to the provision of such services. The Partnership Agreement provides that the General Partner will determine the costs that are allocable to the Partnership in any reasonable manner determined by the General Partner in its sole discretion. Total costs charged to the Partnership by the General Partner were $1 million for the three months ended March 31, 2013 (2012 – $1 million).

As operator, TransCanada’s subsidiaries provide capital and operating services to our pipeline systems. TransCanada’s subsidiaries incur costs on behalf of our pipeline systems, including, but not limited to, employee salary and benefit costs, and property and liability insurance costs.

Capital and operating costs charged to our pipeline systems for the three months ended March 31, 2013 and 2012 by TransCanada’s subsidiaries and amounts payable to TransCanada’s subsidiaries at March 31, 2013 and December 31, 2012 are summarized in the following tables:

	Three months ended
(unaudited)	March 31,
(millions of dollars)	2013	2012

Capital and operating costs charged by TransCanada’s subsidiaries to:
Great Lakes (a)	8	8
Northern Border (a)	7	8
GTN (a)	7	7
Bison (a)	1	2
North Baja	1	1
Tuscarora	1	1
Impact on the Partnership’s net income:
Great Lakes	4	4
Northern Border	3	4
GTN	2	2
Bison	-	1
North Baja	1	1
Tuscarora	1	1

(a) Represents 100 percent of the costs.

(unaudited)
(millions of dollars)	March 31, 2013	December 31, 2012

Amount payable to TransCanada’s subsidiaries for costs charged in the period by:
Great Lakes (a)	3	4
Northern Border (a)	3	4
GTN (a)	2	3
Bison (a)	-	1
North Baja	-	1
Tuscarora	-	1

(a) Represents 100 percent of the costs.

Great Lakes earns transportation revenues from TransCanada and its affiliates under contracts, some of which are provided at discounted rates and some at maximum recourse rates. Great Lakes earned $21 million of transportation revenues under these contracts for the three months ended March 31, 2013 (2012 - $24 million). These amounts represent 59 percent of total revenues earned by Great Lakes for the three months ended March 31, 2013 (2012 – 48 percent).

Revenue from TransCanada and its affiliates of $10 million is included in the Partnership’s equity earnings from Great Lakes for the three months ended March 31, 2013 (2012 - $11 million). At March 31, 2013, $8 million was included in Great Lakes’ receivables in regards to the transportation contracts with TransCanada and its affiliates (December 31, 2012 - $10 million).

- Definition

The entire disclosure for related party transactions. Examples of related party transactions include transactions between (a) a parent company and its subsidiary; (b) subsidiaries of a common parent; (c) and entity and its principal owners; and (d) affiliates.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 850
-SubTopic 10
-Section 50
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-Publisher FASB
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-Name Regulation S-X (SX)
-Number 210
-Section 04
-Paragraph b
-Article 3A

Reference 8: http://www.xbrl.org/2003/role/presentationRef
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-Number 210
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Reference 9: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 57
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-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

+ Details

FAIR VALUE MEASUREMENTS	3 Months Ended
FAIR VALUE MEASUREMENTS	Mar. 31, 2013
FAIR VALUE MEASUREMENTS
FAIR VALUE MEASUREMENTS	NOTE 10 FAIR VALUE MEASUREMENTS (a) Fair Value Hierarchy Under Accounting Standards Codification (ASC) 820, Fair Value Measurements and Disclosures, fair value measurements are characterized in one of three levels based upon the input used to arrive at the measurement. The three levels of the fair value hierarchy are as follows: · Level 1 inputs are quoted prices (unadjusted) in active markets for identical assets or liabilities that we have the ability to access at the measurement date. · Level 2 inputs are inputs other than quoted prices included within Level 1 that are observable for the asset or liability, either directly or indirectly. · Level 3 inputs are unobservable inputs for the asset or liability. When appropriate, valuations are adjusted for various factors including credit considerations. Such adjustments are generally based on available market evidence. In the absence of such evidence, management’s best estimate is used. (b) Fair Value of Financial Instruments The carrying value of cash and cash equivalents, accounts receivable and other, accounts payable and accrued liabilities, accrued interest and the Senior Credit Facility approximate their fair values because of the short maturity or duration of these instruments, or because the instruments bear a variable rate of interest or a rate that approximates current rates. The fair value of the Partnership’s Senior Notes is estimated by discounting the future cash flows of each instrument at estimated current borrowing rates. The estimated fair value of the Partnership’s and its subsidiary’s Senior Notes as of March 31, 2013 is $408 million (December 31, 2012 - $402 million). Senior Notes are recorded at amortized cost and classified in Level 2 of the fair value hierarchy for fair value disclosure purposes.

ACCOUNTS RECEIVABLE AND OTHER

3 Months Ended

Mar. 31, 2013

ACCOUNTS RECEIVABLE AND OTHER

ACCOUNTS RECEIVABLE AND OTHER

NOTE 11 ACCOUNTS RECEIVABLE AND OTHER

(unaudited)
(millions of dollars)	March 31, 2013	December 31, 2012

Accounts receivable	7	8
Inventory	1	1
	8	9

SUBSEQUENT EVENTS	3 Months Ended
SUBSEQUENT EVENTS	Mar. 31, 2013
SUBSEQUENT EVENTS
SUBSEQUENT EVENTS	NOTE 12 SUBSEQUENT EVENTS On April 23, 2013, the board of directors of our General Partner declared the Partnership’s first quarter 2013 cash distribution in the amount of $0.78 per common unit payable on May 15, 2013 to unitholders of record as of May 6, 2013. Great Lakes declared its first quarter 2013 distribution of $12 million on April 18, 2013, of which the Partnership will receive its 46.45 percent share or $6 million on May 1, 2013. Northern Border declared its first quarter 2013 distribution of $44 million on April 18, 2013, of which the Partnership will receive its 50 percent share or $22 million on May 1, 2013. GTN declared its first quarter 2013 distribution of $33 million on April 18, 2013, of which the Partnership will receive its 25 percent share or $8 million on May 1, 2013. Bison declared its first quarter 2013 distribution of $13 million on April 18, 2013, of which the Partnership will receive its 25 percent share or $3 million on May 1, 2013.

SIGNIFICANT ACCOUNTING POLICIES (Policies)	3 Months Ended
SIGNIFICANT ACCOUNTING POLICIES (Policies)	Mar. 31, 2013
SIGNIFICANT ACCOUNTING POLICIES
Basis of Presentation	(a) Basis of Presentation The Partnership uses the equity method of accounting for its investments in Great Lakes, Northern Border, GTN and Bison, over which it is able to exercise significant influence. The Partnership consolidates its investments in North Baja and Tuscarora.
Use of Estimates	(b) Use of Estimates The preparation of financial statements requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities as of the date of the financial statements, and the reported amounts of revenues and expenses during the reporting period. Although management believes these estimates are reasonable, actual results could differ from these estimates.

- Definition

Disclosure of accounting policy regarding (1) the principles it follows in consolidating or combining the separate financial statements, including the principles followed in determining the inclusion or exclusion of subsidiaries or other entities in the consolidated or combined financial statements and (2) its treatment of interests (for example, common stock, a partnership interest or other means of exerting influence) in other entities, for example consolidation or use of the equity or cost methods of accounting. The accounting policy may also address the accounting treatment for intercompany accounts and transactions, noncontrolling interest, and the income statement treatment in consolidation for issuances of stock by a subsidiary.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
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Reference 9: http://www.xbrl.org/2003/role/presentationRef
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Reference 10: http://www.xbrl.org/2003/role/presentationRef
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-Name Accounting Principles Board Opinion (APB)
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-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

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-Name Emerging Issues Task Force (EITF)
-Number 96-16
-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 12: http://www.xbrl.org/2003/role/presentationRef
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Reference 13: http://www.xbrl.org/2003/role/presentationRef
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Reference 14: http://www.xbrl.org/2003/role/presentationRef
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-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 15: http://www.xbrl.org/2003/role/presentationRef
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Reference 16: http://www.xbrl.org/2003/role/presentationRef
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Reference 17: http://www.xbrl.org/2003/role/presentationRef
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Reference 18: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
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Reference 19: http://www.xbrl.org/2003/role/presentationRef
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+ Details

INVESTMENTS IN UNCONSOLIDATED AFFILIATES (Tables)

3 Months Ended

Mar. 31, 2013

INVESTMENTS IN UNCONSOLIDATED AFFILIATES

Schedule of equity method investments in unconsolidated affiliates

	Ownership	Equity Earnings from Unconsolidated Affiliates		Investments in Unconsolidated Affiliates
	Interest at	Three months
(unaudited)	March 31,	ended March 31,		March 31,	December 31,
(millions of dollars)	2013	2013	2012	2013	2012

Great Lakes	46.45%	2	9	677	677
Northern Border (a)	50%	16	20	507	512
GTN	25%	5	6	215	216
Bison	25%	3	3	157	158
		26	38	1,556	1,563

Great Lakes

Investments in unconsolidated affiliates

Summarized financial information for equity method investment

(unaudited)
(millions of dollars)	March 31, 2013	December 31, 2012

ASSETS
Current assets	51	56
Plant, property and equipment, net	792	799
	843	855

Liabilities and Partners’ Equity
Current liabilities	27	30
Long-term debt, including current maturities	345	354
Partners’ equity	471	471
	843	855

	Three months ended
(unaudited)	March 31,
(millions of dollars)	2013		2012

Transmission revenues	35		49
Operating expenses	(15	)	(15	)
Depreciation	(8	)	(8	)
Financial charges and other	(7	)	(7	)
Net income	5		19

Northern Border

Investments in unconsolidated affiliates

Summarized financial information for equity method investment

(unaudited)
(millions of dollars)	March 31, 2013	December 31, 2012

ASSETS
Cash and cash equivalents	34	28
Other current assets	34	35
Plant, property and equipment, net	1,220	1,234
Other assets	31	31
	1,319	1,328

Liabilities and Partners’ Equity
Current liabilities	53	53
Deferred credits and other	17	16
Long-term debt, including current maturities	473	473
Partners’ equity
Partners’ capital	779	789
Accumulated other comprehensive loss	(3)	(3)
	1,319	1,328

	Three months ended
(unaudited)	March 31,
(millions of dollars)	2013		2012

Transmission revenues	72		81
Operating expenses	(19	)	(18	)
Depreciation	(15	)	(16	)
Financial charges and other	(5	)	(6	)
Net income	33		41

GTN

Investments in unconsolidated affiliates

Summarized financial information for equity method investment

(unaudited)
(millions of dollars)	March 31, 2013	December 31, 2012

ASSETS
Current assets	62	50
Plant, property and equipment, net	1,162	1,174
Other assets	1	1
	1,225	1,225

Liabilities and Members’ Equity
Current liabilities	17	16
Deferred credits and other	21	20
Long-term debt, including current maturities	325	325
Members’ capital	862	864
	1,225	1,225

	Three months ended
(unaudited)	March 31,
(millions of dollars)	2013		2012

Transmission revenues	49		52
Operating expenses	(11	)	(11	)
Depreciation	(13	)	(13	)
Financial charges and other	(4	)	(5	)
Net income	21		23

Bison

Investments in unconsolidated affiliates

Summarized financial information for equity method investment

(unaudited)
(millions of dollars)	March 31, 2013	December 31, 2012

ASSETS
Current assets	7	7
Plant, property and equipment, net	645	649
	652	656

Liabilities and Members’ Equity
Current liabilities	25	25
Members’ capital	627	631
	652	656

	Three months ended
(unaudited)	March 31,
(millions of dollars)	2013		2012

Transmission revenues	20		20
Operating expenses	(4	)	(3	)
Depreciation	(5	)	(5	)
Net income	11		12

CREDIT FACILITIES AND LONG-TERM DEBT (Tables)

3 Months Ended

Mar. 31, 2013

CREDIT FACILITIES AND LONG-TERM DEBT

Components of debt

(unaudited)
(millions of dollars)	March 31, 2013	December 31, 2012

Senior Credit Facility due 2017	309	312
4.65% Senior Notes due 2021	349	349
3.82% Series D Senior Notes due 2017	27	27
	685	688
Less: current portion of long-term debt	3	3
	682	685

Principal repayments required by the Partnership on the long-term debt

(unaudited)
(millions of dollars)

2013		3
2014		4
2015		4
2016		4
2017		321
Thereafter		349
		685

NET INCOME PER COMMON UNIT (Tables)

3 Months Ended

Mar. 31, 2013

NET INCOME PER COMMON UNIT

Schedule of net income per common unit

	Three months ended
(unaudited)	March 31,
(millions of dollars, except per unit)	2013		2012

Net income	29		39
Net income allocated to General Partner	(1	)	(1	)
Net income allocable to common units	28		38
Weighted average common units outstanding (millions) – basic and diluted	53.5		53.5
Net income per common unit – basic and diluted	$0.52		$0.71

CHANGE IN WORKING CAPITAL (Tables)

3 Months Ended

Mar. 31, 2013

CHANGE IN WORKING CAPITAL

Summary of change in working capital

(unaudited)	Three months ended March 31,
(millions of dollars)	2013		2012

Decrease in accounts receivable and other	1		1
Increase/(decrease) in accounts payable and accrued liabilities	(2	)	1
Increase in accrued interest	4		5
Decrease in operating working capital	3		7

RELATED PARTY TRANSACTIONS (Tables)

3 Months Ended

Mar. 31, 2013

RELATED PARTY TRANSACTIONS

Schedule of costs charged by related party

	Three months ended
(unaudited)	March 31,
(millions of dollars)	2013	2012

Capital and operating costs charged by TransCanada’s subsidiaries to:
Great Lakes (a)	8	8
Northern Border (a)	7	8
GTN (a)	7	7
Bison (a)	1	2
North Baja	1	1
Tuscarora	1	1
Impact on the Partnership’s net income:
Great Lakes	4	4
Northern Border	3	4
GTN	2	2
Bison	-	1
North Baja	1	1
Tuscarora	1	1

(a) Represents 100 percent of the costs.

Schedule of amounts payable to related party for costs charged during the period

(unaudited)
(millions of dollars)	March 31, 2013	December 31, 2012

Amount payable to TransCanada’s subsidiaries for costs charged in the period by:
Great Lakes (a)	3	4
Northern Border (a)	3	4
GTN (a)	2	3
Bison (a)	-	1
North Baja	-	1
Tuscarora	-	1

(a) Represents 100 percent of the costs.

ACCOUNTS RECEIVABLE AND OTHER (Tables)

3 Months Ended

Mar. 31, 2013

ACCOUNTS RECEIVABLE AND OTHER

Schedule of accounts receivable and other

(unaudited)
(millions of dollars)	March 31, 2013	December 31, 2012

Accounts receivable	7	8
Inventory	1	1
	8	9

INVESTMENTS IN UNCONSOLIDATED AFFILIATES (Details) - USD ($)		1 Months Ended	3 Months Ended
	Jan. 02, 2013	Apr. 30, 2006	Mar. 31, 2013	Mar. 31, 2012	Dec. 31, 2012
Investments in unconsolidated affiliates
Equity Earnings from Unconsolidated Affiliates			$ 26,000,000	$ 38,000,000
Investments in Unconsolidated Affiliates			$ 1,556,000,000		$ 1,563,000,000
Great Lakes
Investments in unconsolidated affiliates
Ownership interest at the end of the period (as a percent)			46.45%
Equity Earnings from Unconsolidated Affiliates			$ 2,000,000	9,000,000
Undistributed earnings			0	0
Investments in Unconsolidated Affiliates			677,000,000		677,000,000
Equity contribution			4,000,000	4,000,000
Total cash call issued to fund debt repayment			9,000,000
Assets
Current assets			51,000,000		56,000,000
Plant, property and equipment, net			792,000,000		799,000,000
Assets, total			843,000,000		855,000,000
Liabilities and Partners' Equity
Current liabilities			27,000,000		30,000,000
Long-term debt, including current maturities			345,000,000		354,000,000
Partners' equity
Partners' equity			471,000,000		471,000,000
Liabilities and Equity, total			843,000,000		855,000,000
Revenues (expenses)
Transmission revenues			35,000,000	49,000,000
Operating expenses			(15,000,000)	(15,000,000)
Depreciation			(8,000,000)	(8,000,000)
Financial charges and other			(7,000,000)	(7,000,000)
Net income			$ 5,000,000	19,000,000
Northern Border
Investments in unconsolidated affiliates
Ownership interest at the end of the period (as a percent)			50.00%
Equity Earnings from Unconsolidated Affiliates			$ 16,000,000	20,000,000
Undistributed earnings			0	0
Investments in Unconsolidated Affiliates			$ 507,000,000		512,000,000
Amortization period of transaction fee			12 years
Transaction fee		$ 10,000,000
Additional ownership interest acquired (as a percent)		20.00%
Assets
Cash and cash equivalents			$ 34,000,000		28,000,000
Other current assets			34,000,000		35,000,000
Plant, property and equipment, net			1,220,000,000		1,234,000,000
Other assets			31,000,000		31,000,000
Assets, total			1,319,000,000		1,328,000,000
Liabilities and Partners' Equity
Current liabilities			53,000,000		53,000,000
Deferred credits and other			17,000,000		16,000,000
Long-term debt, including current maturities			473,000,000		473,000,000
Partners' equity
Partners' equity			779,000,000		789,000,000
Accumulated other comprehensive loss			(3,000,000)		(3,000,000)
Liabilities and Equity, total			1,319,000,000		1,328,000,000
Revenues (expenses)
Transmission revenues			72,000,000	81,000,000
Operating expenses			(19,000,000)	(18,000,000)
Depreciation			(15,000,000)	(16,000,000)
Financial charges and other			(5,000,000)	(6,000,000)
Net income			$ 33,000,000	41,000,000
Reduction in current transportation rates (as a percent)	11.00%
GTN
Investments in unconsolidated affiliates
Ownership interest at the end of the period (as a percent)			25.00%
Equity Earnings from Unconsolidated Affiliates			$ 5,000,000	6,000,000
Undistributed earnings			0	0
Investments in Unconsolidated Affiliates			215,000,000		216,000,000
Assets
Current assets			62,000,000		50,000,000
Plant, property and equipment, net			1,162,000,000		1,174,000,000
Other assets			1,000,000		1,000,000
Assets, total			1,225,000,000		1,225,000,000
Liabilities and Partners' Equity
Current liabilities			17,000,000		16,000,000
Deferred credits and other			21,000,000		20,000,000
Long-term debt, including current maturities			325,000,000		325,000,000
Partners' equity
Partners' equity			862,000,000		864,000,000
Liabilities and Equity, total			1,225,000,000		1,225,000,000
Revenues (expenses)
Transmission revenues			49,000,000	52,000,000
Operating expenses			(11,000,000)	(11,000,000)
Depreciation			(13,000,000)	(13,000,000)
Financial charges and other			(4,000,000)	(5,000,000)
Net income			$ 21,000,000	23,000,000
Bison
Investments in unconsolidated affiliates
Ownership interest at the end of the period (as a percent)			25.00%
Equity Earnings from Unconsolidated Affiliates			$ 3,000,000	3,000,000
Undistributed earnings			0	0
Investments in Unconsolidated Affiliates			157,000,000		158,000,000
Assets
Current assets			7,000,000		7,000,000
Plant, property and equipment, net			645,000,000		649,000,000
Assets, total			652,000,000		656,000,000
Liabilities and Partners' Equity
Current liabilities			25,000,000		25,000,000
Partners' equity
Partners' equity			627,000,000		631,000,000
Liabilities and Equity, total			652,000,000		$ 656,000,000
Revenues (expenses)
Transmission revenues			20,000,000	20,000,000
Operating expenses			(4,000,000)	(3,000,000)
Depreciation			(5,000,000)	(5,000,000)
Net income			$ 11,000,000	$ 12,000,000

CREDIT FACILITIES AND LONG-TERM DEBT (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012	Dec. 31, 2012
Credit facility and long-term debt
Total long-term debt	$ 685		$ 688
Less: current portion of long-term debt	3		3
Long-term debt	682		685
Senior Credit Facility due 2017
Credit facility and long-term debt
Total long-term debt	$ 309		312
Senior Credit Facility due 2017 \| LIBOR-based borrowings
Credit facility and long-term debt
Line of credit facility, base rate	LIBOR	LIBOR
Debt average interest rate (as a percent)	1.46%	1.65%
Debt interest rate at end of period (as a percent)	1.46%	1.63%
Senior revolving credit facility
Credit facility and long-term debt
Maximum borrowing capacity	$ 500
Amount outstanding under credit facility	309		$ 312
Remaining borrowing capacity	$ 191
4.65% Senior Notes due 2021
Credit facility and long-term debt
Stated interest rate (as a percent)	4.65%		4.65%
Total long-term debt	$ 349		$ 349
3.82% Series D Senior Notes due 2017
Credit facility and long-term debt
Stated interest rate (as a percent)	3.82%		3.82%
Total long-term debt	$ 27		$ 27

CREDIT FACILITIES AND LONG-TERM DEBT (Details 2) - USD ($) $ in Millions	Mar. 31, 2013	Dec. 31, 2012
Principal repayments required on the long-term debt
2013	$ 3
2014	4
2015	4
2016	4
2017	321
Thereafter	349
Total long-term debt	$ 685	$ 688

NET INCOME PER COMMON UNIT (Details) shares in Millions, $ in Millions	3 Months Ended
	Mar. 31, 2013 USD ($) $ / shares shares	Mar. 31, 2012 USD ($) $ / shares shares
Common units and interest in the partnership
Net income	$ 29	$ 39
Net income allocated to General Partner	(1)	(1)
Net income allocable to common units	$ 28	$ 38
Weighted average common units outstanding (millions) - basic (in units) \| shares	53.5	53.5
Weighted average common units outstanding (millions) - diluted (in units) \| shares	53.5	53.5
Net income per common unit - basic (in dollars per unit) \| $ / shares	0.52	0.71
Net income per common unit - diluted (in dollars per unit) \| $ / shares	0.52	0.71
General Partner
Common units and interest in the partnership
Additional percentage investment held by General Partner	2.00%

CASH DISTRIBUTIONS (Details) - USD ($)	3 Months Ended
CASH DISTRIBUTIONS (Details) - USD ($)	Mar. 31, 2013	Mar. 31, 2012
Incentive distributions
Cash distributions (in dollars per unit)	$ 0.78	$ 0.77
Cash distribution	$ 43,000,000	$ 42,000,000
General Partner
Incentive distributions
Incentive distributions	$ 0	$ 0

CHANGE IN WORKING CAPITAL (Details) - USD ($) $ in Millions	3 Months Ended
CHANGE IN WORKING CAPITAL (Details) - USD ($) $ in Millions	Mar. 31, 2013	Mar. 31, 2012
CHANGE IN WORKING CAPITAL
Decrease in accounts receivable and other	$ 1	$ 1
Increase/(decrease) in accounts payable and accrued liabilities	(2)	1
Increase in accrued interest	4	5
Decrease/(increase) in operating working capital	$ 3	$ 7

RELATED PARTY TRANSACTIONS (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012	Dec. 31, 2012
General Partner
Costs charged to the pipeline system and amounts payable
Costs charged by TransCanada and its affiliates	$ 1	$ 1
TransCanada Corporation \| Great Lakes
Costs charged to the pipeline system and amounts payable
Costs charged by TransCanada and its affiliates	8	8
Impact on the Partnership's net income	4	4
Amounts payable to TransCanada and its affiliates	$ 3		$ 4
Percentage of capital and operating costs charged by TransCanada's subsidiaries	100.00%
Transportation revenues from TransCanada and its affiliates	$ 21	$ 24
Percentage of transportation revenues to total revenues	59.00%	48.00%
Revenue from TransCanada and its affiliates included in the Partnership's equity earnings from Great Lakes	$ 10	$ 11
Great Lakes' receivables for transportation contracts with TransCanada and its affiliates	8		10
TransCanada Corporation \| Northern Border
Costs charged to the pipeline system and amounts payable
Costs charged by TransCanada and its affiliates	7	8
Impact on the Partnership's net income	3	4
Amounts payable to TransCanada and its affiliates	$ 3		4
Percentage of capital and operating costs charged by TransCanada's subsidiaries	100.00%
TransCanada Corporation \| GTN
Costs charged to the pipeline system and amounts payable
Costs charged by TransCanada and its affiliates	$ 7	7
Impact on the Partnership's net income	2	2
Amounts payable to TransCanada and its affiliates	$ 2		3
Percentage of capital and operating costs charged by TransCanada's subsidiaries	100.00%
TransCanada Corporation \| Bison
Costs charged to the pipeline system and amounts payable
Costs charged by TransCanada and its affiliates	$ 1	2
Impact on the Partnership's net income		1
Amounts payable to TransCanada and its affiliates			1
Percentage of capital and operating costs charged by TransCanada's subsidiaries	100.00%
TransCanada Corporation \| North Baja
Costs charged to the pipeline system and amounts payable
Costs charged by TransCanada and its affiliates	$ 1	1
Impact on the Partnership's net income	1	1
Amounts payable to TransCanada and its affiliates			1
TransCanada Corporation \| Tuscarora
Costs charged to the pipeline system and amounts payable
Costs charged by TransCanada and its affiliates	1	1
Impact on the Partnership's net income	$ 1	$ 1
Amounts payable to TransCanada and its affiliates			$ 1

FAIR VALUE MEASUREMENTS (Details) - USD ($) $ in Millions	Mar. 31, 2013	Dec. 31, 2012
Fair Value
Financial Instruments
Long-term debt	$ 408	$ 402

ACCOUNTS RECEIVABLE AND OTHER (Details) - USD ($) $ in Millions	Mar. 31, 2013	Dec. 31, 2012
ACCOUNTS RECEIVABLE AND OTHER
Accounts receivable	$ 7	$ 8
Inventory	1	1
Accounts receivable and other	$ 8	$ 9

SUBSEQUENT EVENTS (Details) - USD ($) $ / shares in Units, $ in Millions	May 02, 2013	Apr. 23, 2013	Apr. 18, 2013	Mar. 31, 2013
Great Lakes
Subsequent events
Ownership interest (as a percent)				46.45%
Northern Border
Subsequent events
Ownership interest (as a percent)				50.00%
GTN
Subsequent events
Ownership interest (as a percent)				25.00%
Bison
Subsequent events
Ownership interest (as a percent)				25.00%
Subsequent event \| Cash distribution declared
Subsequent events
Cash distribution (in dollars per unit)		$ 0.78
Subsequent event \| Cash distribution declared \| Great Lakes
Subsequent events
Aggregate distribution declared and payable by investee			$ 12
Subsequent event \| Cash distribution declared \| Northern Border
Subsequent events
Aggregate distribution declared and payable by investee			44
Subsequent event \| Cash distribution declared \| GTN
Subsequent events
Aggregate distribution declared and payable by investee			33
Subsequent event \| Cash distribution declared \| Bison
Subsequent events
Aggregate distribution declared and payable by investee			$ 13
Subsequent event \| Cash Distribution Paid \| Great Lakes \| Expected
Subsequent events
Ownership interest (as a percent)	46.45%
Partnership's share of distributions declared and payable by investee	$ 6
Subsequent event \| Cash Distribution Paid \| Northern Border \| Expected
Subsequent events
Ownership interest (as a percent)	50.00%
Partnership's share of distributions declared and payable by investee	$ 22
Subsequent event \| Cash Distribution Paid \| GTN \| Expected
Subsequent events
Ownership interest (as a percent)	25.00%
Partnership's share of distributions declared and payable by investee	$ 8
Subsequent event \| Cash Distribution Paid \| Bison \| Expected
Subsequent events
Ownership interest (as a percent)	25.00%
Partnership's share of distributions declared and payable by investee	$ 3