TC Pipelines (TCP) 10-Q 8 May 15 2015 Q1 Quarterly report Financial data

Document_and_Entity_Informatio

Document and Entity Information	3 Months Ended
	Mar. 31, 2015	1-May-15
Document and Entity Information
Entity Registrant Name	TC PIPELINES LP
Entity Central Index Key	1075607
Document Type	10-Q
Document Period End Date	31-Mar-15
Amendment Flag	FALSE
Current Fiscal Year End Date	-19
Entity Current Reporting Status	Yes
Entity Filer Category	Large Accelerated Filer
Entity Common Stock, Shares Outstanding		63,820,547
Document Fiscal Year Focus	2015
Document Fiscal Period Focus	Q1

CONSOLIDATED_STATEMENTS_OF_INC

CONSOLIDATED STATEMENTS OF INCOME (USD $)	3 Months Ended
In Millions, except Per Share data, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014
CONSOLIDATED STATEMENTS OF INCOME
Transmission revenues	$87	$87
Equity earnings from unconsolidated affiliates (Note 4)	31	33
Operation and maintenance expenses	-11	-12
Property taxes	-6	-6
General and administrative	-3	-2
Depreciation	-21	-21
Financial charges and other	-13	-12
Net income	64	67
Net income attributable to non-controlling interests	7	10
Net income attributable to controlling interests	57	57
Net income attributable to controlling interests allocation (Note 7)
Common units	56	56
General Partner	1	1
Net income allocated to partners	$57	$57
Net income per common unit (Note 7) - basic (in dollars per unit)	$0.88	$0.90
Net income per common unit (Note 7) - diluted (in dollars per unit)	$0.88	$0.90
Weighted average common units outstanding (millions) - basic (in units)	63.6	62.3
Weighted average common units outstanding (millions) - diluted (in units)	63.6	62.3
Common units outstanding, end of period (millions) (in units)	63.6	62.3

CONSOLIDATED_STATEMENTS_OF_COM

CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (USD $)	3 Months Ended
In Millions, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014
CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME
Net income	$64	$67
Other comprehensive income
Reclassification to net income of gains and losses on cash flow hedges (Note 11)	-1
Other comprehensive income	-1
Total comprehensive income	63	67
Comprehensive income attributable to non-controlling interests	7	10
Comprehensive income attributable to controlling interests	$56	$57

CONSOLIDATED_BALANCE_SHEETS

CONSOLIDATED BALANCE SHEETS (USD $)	Mar. 31, 2015	Dec. 31, 2014
In Millions, unless otherwise specified
Current Assets
Cash and cash equivalents	$384	$26
Accounts receivable and other (Note 12)	35	35
Inventories	8	7
Total current assets	427	68
Investments in unconsolidated affiliates (Note 4)	1,183	1,177
Plant, property and equipment (Net of $757 accumulated depreciation; 2014 - $737	1,950	1,968
Goodwill	130	130
Other assets	8	6
Total assets	3,698	3,349
Current Liabilities
Accounts payable and accrued liabilities	27	23
Accounts payable to affiliates (Note 10)	8	15
Accrued interest	13	4
Short-term loan (Note 5)	170	170
Current portion of long-term debt (Note 5)	79	79
Total current liabilities	297	291
Long-term debt (Note 5)	1,785	1,446
Other liabilities	27	26
Total liabilities	2,109	1,763
Partners' Equity
Common units	1,331	1,325
General partner	29	29
Accumulated other comprehensive loss	-3	-2
Controlling interests	1,357	1,352
Non-controlling interests	232	234
Total partners' equity	1,589	1,586
Total liabilities and partners' equity	$3,698	$3,349

CONSOLIDATED_BALANCE_SHEET_Par

CONSOLIDATED BALANCE SHEET (Parenthetical) (USD $)	Mar. 31, 2015	Dec. 31, 2014
In Millions, unless otherwise specified
CONSOLIDATED BALANCE SHEETS
Accumulated depreciation	$757	$737

CONSOLIDATED_STATEMENTS_OF_CAS

CONSOLIDATED STATEMENTS OF CASH FLOWS (USD $)	3 Months Ended
In Millions, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014
Cash Generated From Operations
Net income	$64	$67
Depreciation	21	21
Amortization of debt issue costs	1
Accruals for costs related to the 2015 Acquisition (Note 13)	2
Change in operating working capital (Note 9)	3	16
Total cash generated from operations	87	97
Investing Activities
Capital expenditures	-3	-2
Total investing activities	-5	-6
Financing Activities
Distributions paid (Note 8)	-55	-52
Distributions paid to non-controlling interests	-9	-13
Long-term debt issued, net of discount	349
Long-term debt repaid	-10	-10
Debt issuance costs	-2
Total financing activities	276	-75
Increase/(decrease) in cash and cash equivalents	358	16
Cash and cash equivalents, beginning of period	26	25
Cash and cash equivalents, end of period	384	41
ATM Equity Issuance Program
Financing Activities
Equity issuance, net (Note 6)	3
Northern Border
Cash Generated From Operations
Equity earnings in excess of cumulative distributions		-2
Investing Activities
Cumulative distributions in excess of equity earnings	2
Great Lakes
Cash Generated From Operations
Equity earnings in excess of cumulative distributions	-4	-5
Investing Activities
Investment	($4)	($4)

CONSOLIDATED_STATEMENT_OF_CHAN

CONSOLIDATED STATEMENT OF CHANGES IN PARTNERS' EQUITY (USD $)	Common Units (Limited Partners)	Common Units (Limited Partners)	General Partner	Accumulated Other Comprehensive Loss		Non-controlling interests	ATM Equity Issuance Program	Total
In Millions, unless otherwise specified	ATM Equity Issuance Program
Partners' Equity at beginning of year at Dec. 31, 2014		$1,325	$29	($2)		$234		$1,586
Partners' Equity at beginning of year (in units) at Dec. 31, 2014		63.6
Increase (Decrease) in Partners' Equity
Net income		56	1			7		64
Other comprehensive loss				-1				-1
Equity issuance, net (Note 6)	3						3
Distributions paid		-53	-1			-9		-63
Partners' Equity at end of year at Mar. 31, 2015		$1,331	$29	($3)	[1]	$232		$1,589
Partners' Equity at End of Year (in units) at Mar. 31, 2015		63.6
[1]	Losses related to cash flow hedges reported in Accumulated Other Comprehensive Loss and expected to be reclassified to Net Income in the next 12 months are estimated to be $1 million. These estimates assume constant interest rates over time; however, the amounts reclassified will vary based on actual value of interest rates at the date of settlement.

CONSOLIDATED_STATEMENT_OF_CHAN1

CONSOLIDATED STATEMENT OF CHANGES IN PARTNERS' EQUITY (Parenthetical) (USD $)	3 Months Ended
In Millions, unless otherwise specified	Mar. 31, 2015
Losses related to cash flow hedges reported in Accumulated Other Comprehensive Loss
Losses expected to be reclassified to net income in the next 12 months	$1

ORGANIZATION

ORGANIZATION	3 Months Ended
	Mar. 31, 2015
ORGANIZATION
ORGANIZATION
	NOTE 1ORGANIZATION
	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_POLICIE

SIGNIFICANT ACCOUNTING POLICIES	3 Months Ended
	Mar. 31, 2015
SIGNIFICANT ACCOUNTING POLICIES
SIGNIFICANT ACCOUNTING POLICIES
	NOTE 2SIGNIFICANT 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, 2015 and 2014 are not necessarily indicative of the results that may be expected for the 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, 2014. That report contains a more comprehensive summary of the Partnership’s significant 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, 2014. 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 consolidates its investments in GTN, Bison, North Baja and Tuscarora, over which it is able to exercise control. To the extent there are interests owned by other parties, these interests are included in non-controlling interests. The Partnership uses the equity method of accounting for its investments in Northern Border and Great Lakes, over which it is able to exercise significant influence.
	(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

ACCOUNTING PRONOUNCEMENTS	3 Months Ended
	Mar. 31, 2015
ACCOUNTING PRONOUNCEMENTS
ACCOUNTING PRONOUNCEMENTS
	NOTE 3ACCOUNTING PRONOUNCEMENTS
	Revenue from contracts with customers
	In May 2014, the FASB issued new guidance on Revenue from Contracts with Customers (Topic 606). This guidance supersedes the revenue recognition requirements in Topic 605, Revenue Recognition and most industry-specific guidance. This new guidance requires that an entity recognizes revenue to depict the transfer of promised goods or services to customers in an amount that reflects the consideration to which the company expects to be entitled in exchange for those goods or services. This new guidance is effective from January 1, 2017 with two methods in which the amendment can be applied; (1) retrospectively to each prior reporting period presented, or (2) retrospectively with the cumulative effect recognized at the date of initial application.   On April 1, 2015, the FASB proposed deferring the effective date by one year to December 15, 2017 for annual reporting periods beginning after that date. The FASB also proposed permitting early adoption of the standard, but not before the original effective date of December 15, 2016. The Partnership is currently evaluating the impact of the adoption of this Accounting Standards Update (ASU) and has not yet determined the effect on its consolidated financial statements.
	Consolidation
	In February 2015, the FASB issued an amendment of previously issued guidance on consolidation (Topic 810). This updated guidance requires that an entity evaluate whether it should consolidate certain legal entities. All legal entities are subject to reevaluation under the revised consolidation model. This guidance is effective from January 1, 2016 and early application is permitted. Application of this amendment could be performed using a modified retrospective approach by recording a cumulative-effect adjustment to equity as of the beginning of the fiscal year of adoption. Alternatively, the amendment could be applied retrospectively. The Partnership is currently evaluating the impact of the adoption of this ASU and has not yet determined the effect on its consolidated financial statements.
	Imputation of interest
	In April 2015, the FASB issued an amendment of previously issued guidance on imputation of interest (Subtopic 835-30). This updated guidance requires debt issuance costs be presented in the balance sheet as a direct deduction from the carrying amount of debt liabilities, consistent with debt discount or premiums.  The recognition and measurement for debt issuance costs would not be affected. This guidance is effective from January 1, 2016 and early application is permitted. This guidance should be adopted on a retrospective basis, wherein the balance sheet of each individual period presented would be adjusted to reflect the period-specific effects of applying the new guidance. The application of this amendment will result in a reclassification of debt issuance costs currently recorded in Other Assets to an offset of their respective debt liabilities.

INVESTMENTS_IN_UNCONSOLIDATED_

INVESTMENTS IN UNCONSOLIDATED AFFILIATES	3 Months Ended
	Mar. 31, 2015
INVESTMENTS IN UNCONSOLIDATED AFFILIATES
INVESTMENTS IN UNCONSOLIDATED AFFILIATES
	NOTE 4INVESTMENTS IN UNCONSOLIDATED AFFILIATES
	Northern Border and Great Lakes 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			Investments in
					Unconsolidated Affiliates			Unconsolidated Affiliates
			Interest at		Three months
	(unaudited)		March 31,		ended March 31,			March 31,	December 31,
	(millions of dollars)		2015		2015		2014	2015	2014
	Northern Border(a)		50%		20		23	503	505
	Great Lakes		46.45%		11		10	680	672
					31		33	1,183	1,177
		(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.
	Northern Border
	The Partnership recorded no undistributed earnings from Northern Border for the three months ended March 31, 2015 and 2014.
	The summarized financial information for Northern Border is as follows:
	(unaudited)
	(millions of dollars)		March 31, 2015			December 31, 2014
	ASSETS
	Cash and cash equivalents		51			41
	Other current assets		36			34
	Plant, property and equipment, net		1,150			1,163
	Other assets		33			34
			1,270			1,272
	LIABILITIES AND PARTNERS’ EQUITY
	Current liabilities		65			64
	Deferred credits and other		23			22
	Long-term debt, including current maturities		411			411
	Partners’ equity
	Partners’ capital		773			777
	Accumulated other comprehensive loss		(2	)		(2	)
			1,270			1,272
			Three months ended
	(unaudited)		March 31,
	(millions of dollars)		2015			2014
	Transmission revenues		75			86
	Operating expenses		(16	)		(18	)
	Depreciation		(15	)		(15	)
	Financial charges and other		(5	)		(6	)
	Net income		39			47
	Great Lakes
	The Partnership made an equity contribution to Great Lakes of $4 million in the first quarter of 2015. 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, 2015 and 2014.
	The summarized financial information for Great Lakes is as follows:
	(unaudited)
	(millions of dollars)		March 31, 2015			December 31, 2014
	ASSETS
	Current assets		88			66
	Plant, property and equipment, net		741			748
			829			814
	LIABILITIES AND PARTNERS’ EQUITY
	Current liabilities		45			38
	Long-term debt, including current maturities		307			316
	Partners’ equity		477			460
			829			814
			Three months ended
	(unaudited)		March 31,
	(millions of dollars)		2015			2014
	Transmission revenues		48			48
	Operating expenses		(11	)		(12	)
	Depreciation		(7	)		(7	)
	Financial charges and other		(6	)		(7	)
	Net income		24			22

CREDIT_FACILITIES_SHORTTERM_LO

CREDIT FACILITIES, SHORT-TERM LOAN FACILITY AND LONG-TERM DEBT	3 Months Ended
	Mar. 31, 2015
CREDIT FACILITIES, SHORT-TERM LOAN FACILITY AND LONG-TERM DEBT
CREDIT FACILITIES, SHORT-TERM LOAN FACILITY AND LONG-TERM DEBT
	NOTE 5CREDIT FACILITIES, SHORT-TERM LOAN FACILITY AND LONG-TERM DEBT
	(unaudited)
	(millions of dollars)	March 31, 2015	December 31, 2014
	Senior Credit Facility due 2017	320	330
	Term Loan Facility due 2018	500	500
	Short-Term Loan Facility due 2015	170	170
	4.65% Unsecured Senior Notes due 2021, net of discount	350	350
	(2015 and 2014 – nil)
	4.375% Unsecured Senior Notes due 2025, net of $1 million discount	349	-
	5.09% Unsecured Senior Notes due 2015	75	75
	5.29% Unsecured Senior Notes due 2020	100	100
	5.69% Unsecured Senior Notes due 2035	150	150
	3.82% Series D Senior Notes due 2017	20	20
		2,034	1,695
	Less: current portion	249	249
		1,785	1,446
	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 $320 million was outstanding at March 31, 2015 (December 31, 2014 - $330 million), leaving $180 million available for future borrowing.
	The London Interbank Offered Rate (LIBOR) based interest rate on the Senior Credit Facility averaged 1.43 percent for the three months ended March 31, 2015 (2014 – 1.42 percent). The LIBOR-based interest rate was 1.43 percent at March 31, 2015 (December 31, 2014 – 1.41 percent).
	The LIBOR-based interest rate on the Term Loan Facility due 2018 averaged 1.43 percent for the three months ended March 31, 2015 (2014 – 1.42 percent). After hedging activity, the interest rate incurred on the Term Loan Facility averaged 1.83 percent for three months ended March 31, 2015 (2014 – 1.83 percent). Prior to hedging activities, the LIBOR-based interest rate was 1.43 percent at March 31, 2015 (December 31, 2014 – 1.41 percent).
	The LIBOR-based interest rate on the Short-Term Loan Facility averaged 1.30 percent for the three months ended March 31, 2015 and was 1.30 percent at March 31, 2015.
	The Senior Credit Facility, the Term Loan Facilities and Short-Term Loan Facility require the Partnership to maintain a certain leverage ratio (debt to adjusted cash flow [net income plus cash distributions received, extraordinary losses, interest expense, expense for taxes paid or accrued, and depreciation and amortization expense less equity earnings and extraordinary gains]).  In the quarter in which an acquisition has occurred, and the two quarters following the acquisition, the allowable leverage ratio increases to 5.50 to 1.00. Thereafter, the ratio returns to 5.00 to 1.00. The allowable ratio for the quarter ended March 31, 2015 is 5.50 to 1.00. The leverage ratio was 5.20 to 1.00 as of March 31, 2015 which included the impact of the issuance of the $350 million senior unsecured notes.  As of April 1, 2015, in connection with closing of the 2015 GTN Acquisition, the leverage ratio was reduced to 4.97 to 1.00.
	On March 13, 2015, the Partnership closed a $350 million public offering of senior unsecured notes bearing an interest rate of 4.375 percent maturing March 13, 2025. The net proceeds of $346 million were used to fund a portion of the acquisition of the remaining 30 percent interest of GTN (2015 GTN Acquisition – refer to Note 13) and to reduce the amount outstanding under our Senior Credit Facility.  The indenture for the notes contains customary investment grade covenants.
	On June 1, 2015, GTN’s 5.09 percent unsecured Senior Notes will mature.  As market conditions dictate, GTN intends to refinance all or portion of this debt with either fixed-rate or variable rate debt. GTN’s Senior Notes provisions contain a covenant that limits total debt to no greater than 70 percent of total capitalization.
	The Series D Senior Notes, which require yearly principal payment until maturity, are secured by Tuscarora’s transportation contracts, supporting agreements and substantially all of Tuscarora’s property. The note purchase agreements contain certain provisions that include, among other items, limitations on additional indebtedness and distributions to partners.
	At March 31, 2015, 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.
	The principal repayments required of the Partnership on its debt are as follows:
	(unaudited)
	(millions of dollars)
	2015	249
	2016	4
	2017	332
	2018	500
	2019	-
	2020	100
	Thereafter	849
		2,034

PARTNERS_EQUITY

PARTNERS' EQUITY	3 Months Ended
	Mar. 31, 2015
PARTNERS' EQUITY
PARTNERS' EQUITY
	NOTE 6PARTNERS’ EQUITY
	ATM equity issuance program (ATM program)
	In August 2014, the Partnership entered into an Equity Distribution Agreement (the EDA) with five different financial institutions (Managers), pursuant to which the Partnership may from time to time, offer and sell common units having an aggregate offering price of up to $200 million.  Sales of such common units will be made by means of ordinary brokers’ transactions on the NYSE at market prices, in block transactions or as otherwise agreed upon by one or more of the Managers and the Partnership.
	During the three months ended March 31, 2015, the Partnership issued 54,701 common units under the ATM program generating net proceeds of approximately $3.4 million, plus approximately $0.1 million from the General Partner to maintain its effective two percent interest. The commissions to our sales agents were approximately $34 thousand. The net proceeds were used for general partnership purposes.

NET_INCOME_PER_COMMON_UNIT

NET INCOME PER COMMON UNIT	3 Months Ended
	Mar. 31, 2015
NET INCOME PER COMMON UNIT
NET INCOME PER COMMON UNIT
	NOTE 7NET INCOME PER COMMON UNIT
	Net income per common unit is computed by dividing net income attributable to controlling interests, after deduction of the General Partner’s 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. For the three months ended March 31, 2015, incentive distributions allocated to the General Partner were $0.3 million. No incentive distributions were allocated to the General Partner for the three months ended March 31, 2014.
	Net income per common unit was determined as follows:
			Three months ended
	(unaudited)		March 31,
	(millions of dollars, except per common unit amounts)		2015		2014
	Net income attributable to controlling interests		57		57
	Net income allocated to General Partner, including incentive distribution rights (IDRs) (a)		1		1
	Net income allocable to common units		56		56
	Weighted average common units outstanding (millions) – basic and diluted (b)		63.6		62.3
	Net income per common unit – basic and diluted		$		$
			0.88		0.90
		(a)		In the calculation of basic and diluted net income per common unit, the net income allocated to the General Partner includes IDRs pertaining to the current reporting period, but declared and paid in the subsequent period.
		(b)		Under the ATM program, the Partnership has issued 1,288,481 common units.

CASH_DISTRIBUTIONS

CASH DISTRIBUTIONS	3 Months Ended
	Mar. 31, 2015
CASH DISTRIBUTIONS
CASH DISTRIBUTIONS
	NOTE 8CASH DISTRIBUTIONS
	For the three months ended March 31, 2015, the Partnership distributed $0.84 per common unit (2014 – $0.81 per common unit) for a total of $55 million (2014 - $52 million). The distributions paid for the three months ended March 31, 2015 included incentive distribution to the General Partners of approximately $0.3 million.  There were no incentive distributions paid to the General Partner for the three months ended March 31, 2014.

CHANGE_IN_OPERATING_WORKING_CA

CHANGE IN OPERATING WORKING CAPITAL	3 Months Ended
	Mar. 31, 2015
CHANGE IN OPERATING WORKING CAPITAL
CHANGE IN OPERATING WORKING CAPITAL
	NOTE 9CHANGE IN OPERATING WORKING CAPITAL
	(unaudited)	Three months ended March 31,
	(millions of dollars)	2015		2014
	Change in accounts receivable and other	(1	)	3
	Change in accounts payable and accrued liabilities	2		4
	Change in accounts payable to affiliates	(7	)	1
	Change in accrued interest	9		8
	Change in operating working capital	3		16

RELATED_PARTY_TRANSACTIONS

RELATED PARTY TRANSACTIONS	3 Months Ended
	Mar. 31, 2015
RELATED PARTY TRANSACTIONS
RELATED PARTY TRANSACTIONS
	NOTE 10RELATED 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, 2015 (2014 – $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, 2015 and 2014 by TransCanada’s subsidiaries and amounts payable to TransCanada’s subsidiaries at March 31, 2015 and December 31, 2014 are summarized in the following tables:
			Three months ended
	(unaudited)		March 31,
	(millions of dollars)		2015		2014
	Capital and operating costs charged by TransCanada’s subsidiaries to:
	GTN (a)		6		6
	Northern Border (a)		7		7
	Bison (a)		1		1
	Great Lakes (a)		6		7
	North Baja		1		1
	Tuscarora		1		1
	Impact on the Partnership’s net income attributable to controlling interests:
	GTN		4		4
	Northern Border		3		4
	Bison		1		1
	Great Lakes		3		3
	North Baja		1		1
	Tuscarora		1		1
		(a)		Represents 100 percent of the costs.
	(unaudited)
	(millions of dollars)		March 31, 2015		December 31, 2014
	Amount payable to TransCanada’s subsidiaries for costs charged in the period by:
	GTN (a)		5		10
	Northern Border (a)		4		10
	Bison		1		2
	Great Lakes (a)		4		9
	North Baja		1		1
	Tuscarora		1		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 $29 million of transportation revenues under these contracts for the three months ended March 31, 2015 (2014 - $22 million). These amounts represent 61 percent of total revenues earned by Great Lakes for the three months ended March 31, 2015 (2014 – 47 percent).
	Revenue from TransCanada and its affiliates of $14 million is included in the Partnership’s equity earnings from Great Lakes for the three months ended March 31, 2015 (2014 - $11 million). At March 31, 2015, $11 million was included in Great Lakes’ receivables in regards to the transportation contracts with TransCanada and its affiliates (December 31, 2014 - $15 million).
	Effective November 1, 2014, Great Lakes executed contracts with its affiliate, ANR Pipeline Company (ANR) to provide firm service in Michigan and Wisconsin.  These contracts were at the maximum FERC authorized rate and were intended to replace historical contracts.  On December 3, 2014, the FERC accepted and suspended Great Lakes’ tariff records to become effective May 3, 2015, subject to refund.  On January 2, 2015, Great Lakes submitted a request for rehearing and clarification with FERC.  On February 2, 2015, FERC issued an Order granting rehearing to allow for additional time for FERC to consider the request.  On April 20, 2015, ANR filed a settlement with FERC that included an agreement by  ANR to pay Great Lakes the difference between the historical and maximum rates, subject to approval by FERC. Until Great Lakes obtains clarification from FERC or  the settlement is approved, it is providing service to ANR under multiple service agreements and rates.  Great Lakes has deferred approximately $9.4 million of revenue related to services performed in 2014 and has deferred approximately $14 million of revenue related to services performed in 2015 under such agreements that may not ultimately be collected if the settlement is not approved by FERC.

FAIR_VALUE_MEASUREMENTS

FAIR VALUE MEASUREMENTS	3 Months Ended
	Mar. 31, 2015
FAIR VALUE MEASUREMENTS
FAIR VALUE MEASUREMENTS
	NOTE 11FAIR 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 inputs 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, accounts payable to affiliates and accrued interest 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 long-term debt is estimated by discounting the future cash flows of each instrument at estimated current borrowing rates. The fair value of interest rate derivatives is calculated using the income approach which uses period-end market rates and applies a discounted cash flow valuation model.
	The estimated fair value of the Partnership’s debt as at March 31, 2015 and December 31, 2014 are as follows:
	(unaudited)		March 31, 2015			December 31, 2014
	(millions of dollars)		Carrying Value		Fair Value	Carrying Value	Fair Value
	Senior Credit Facility due 2017		320		320	330	330
	Term Loan Facility due 2018		500		500	500	500
	Short-Term Loan Facility due 2015		170		170	170	170
	4.65% Senior Notes due 2021, net		350		368	350	375
	4.375% Senior Notes due 2025, net		349		353	-	-
	5.09% Unsecured Senior Notes due 2015		75		76	75	76
	5.29% Unsecured Senior Notes due 2020		100		112	100	111
	5.69% Unsecured Senior Notes due 2035		150		169	150	168
	3.82% Series D Senior Notes due 2017		20		21	20	21
			2,034		2,089	1,695	1,751
	Long-term debt is recorded at amortized cost and classified in Level II of the fair value hierarchy for fair value disclosure purposes. Interest rate derivative assets and liabilities are classified in Level II for all periods presented where the fair value is determined by using valuation techniques that refer to observable market data or estimated market prices.
	Market risk is the risk that changes in market interest rates may result in fluctuations in the fair values or cash flows of financial instruments. The Partnership’s floating rate debt is subject to LIBOR benchmark interest rate risk. The Partnership uses interest rate derivatives to manage its exposure to interest rate risk. We regularly assess the impact of interest rate fluctuations on future cash flows and evaluate hedging opportunities to mitigate our interest rate risk.
	The interest rate swaps are structured such that the cash flows of the derivative instruments match those of the variable rate of interest on the Term Loan Facility. The Partnership hedged interest payments on $150 million of variable-rate Term Loan Facility with interest rate swaps effective September 3, 2013 and maturing July 1, 2018, at a weighted average fixed interest rate of 2.79 percent. At March 31, 2015, the fair value of the interest rate swaps accounted for as cash flow hedges was a liability of $2 million (both on a gross and net basis) (December 31, 2014 - $1 million). The Partnership did not record any amounts in net income related to ineffectiveness for interest rate hedges for the three months ended March 31, 2015 (2014 – nil). The change in fair value of interest rate derivative instruments recognized in other comprehensive income was a loss of $1 million for the three months ended March 31, 2015 (2014 – less than $1 million). For the three months ended March 31, 2015, the net realized loss related to the interest rate swaps was $1 million and was included in financial charges and other (2014 – $1 million).
	The Partnership has no master netting agreements; however, contracts contain provisions with rights of offset. The Partnership has elected to present the fair value of derivative instruments with the right to offset on a gross basis in the balance sheet. Had the Partnership elected to present these instruments on a net basis, there would be no effect on the consolidated balance sheet as of March 31, 2015 and December 31, 2014.

ACCOUNTS_RECEIVABLE_AND_OTHER

ACCOUNTS RECEIVABLE AND OTHER	3 Months Ended
	Mar. 31, 2015
ACCOUNTS RECEIVABLE AND OTHER
ACCOUNTS RECEIVABLE AND OTHER
	NOTE 12ACCOUNTS RECEIVABLE AND OTHER
	(unaudited)
	(millions of dollars)	March 31, 2015	December 31, 2014
	Trade accounts receivable, net of allowance of nil	30	30
	Accounts receivable from affiliates	1	1
	Other	4	4
		35	35

SUBSEQUENT_EVENTS

SUBSEQUENT EVENTS	3 Months Ended
	Mar. 31, 2015
SUBSEQUENT EVENTS
SUBSEQUENT EVENTS
	NOTE 13SUBSEQUENT EVENTS
	Management of the Partnership has reviewed subsequent events through May 8, 2015, the date the financial statements were issued, and concluded there were no events or transactions during this period that would require recognition or disclosure in the consolidated financial statements other than what is disclosed here and/or those already disclosed in the preceding notes.
	On April 1, 2015, the Partnership acquired the remaining 30 percent interest in GTN from a subsidiary of TransCanada for $446 million plus purchase price adjustments of $10 million. The purchase price consisted of $263 million in cash (including preliminary purchase price adjustments of $10 million), the assumption of $98 million in proportional GTN debt and the issuance of $95 million of new Class B units to TransCanada.
	The Partnership funded the cash portion of the transaction using a portion of the proceeds received on our March 13, 2015 debt offering. The Class B units will be entitled to distribution based on 30 percent of GTN’s annual distributions as follows: i) for the first five years, 100 percent of distributions above $20 million; and ii) for subsequent years, 25 percent of distributions above $20 million.
	The 2015 GTN Acquisition, which resulted in GTN being wholly-owned by the Partnership, will continue to be accounted for as a transaction between entities under common control, similar to pooling of interests, whereby the acquired interest will be recorded at TransCanada’s carrying value and the total excess purchase price paid will be recorded as a reduction in Partners’ Equity.
	On April 23, 2015, the board of directors of our General Partner declared the Partnership’s first quarter 2015 cash distribution in the amount of $0.84 per common unit payable on May 15, 2015 to unitholders of record as of May 5, 2015.
	GTN declared its first quarter 2015 distribution of $37 million on April 21, 2015. The Partnership will receive its 100 percent share on May 1, 2015.
	Northern Border declared its first quarter 2015 distribution of $52 million on April 21, 2015, of which the Partnership will receive its 50 percent share or $26 million on May 1, 2015.
	Great Lakes declared its first quarter 2015 distribution of $30 million on April 21, 2015, of which the Partnership will receive its 46.45 percent share or $14 million on May 1, 2015.
	On April 23, 2015, GTN filed a rate settlement with FERC to satisfy GTN’s obligations from its 2011 rate settlement for new rates to be in effect on January 1, 2016.  The 2015 settlement, if approved, will reduce rates on the mainline by 3 percent on July 1, 2015.  In January, 2016, GTN’s rates will decrease a further 10 percent through December 31, 2019.  Unless superseded by a subsequent rate case or settlement, GTN’s rates will decrease an additional 8 percent for the period January 1, 2020 through December 31, 2021 when GTN will be required to establish new rates.  We expect that GTN’s near term results will not be materially affected due to increased contracting and other revenue opportunities on the system.

SIGNIFICANT_ACCOUNTING_POLICIE1

SIGNIFICANT ACCOUNTING POLICIES (Policies)	3 Months Ended
	Mar. 31, 2015
SIGNIFICANT ACCOUNTING POLICIES
Basis of Presentation
	(a) Basis of Presentation
	The Partnership consolidates its investments in GTN, Bison, North Baja and Tuscarora, over which it is able to exercise control. To the extent there are interests owned by other parties, these interests are included in non-controlling interests. The Partnership uses the equity method of accounting for its investments in Northern Border and Great Lakes, over which it is able to exercise significant influence.
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.

INVESTMENTS_IN_UNCONSOLIDATED_1

INVESTMENTS IN UNCONSOLIDATED AFFILIATES (Tables)	3 Months Ended
	Mar. 31, 2015
INVESTMENTS IN UNCONSOLIDATED AFFILIATES
Schedule of investments in unconsolidated affiliates
			Ownership		Equity Earnings from			Investments in
					Unconsolidated Affiliates			Unconsolidated Affiliates
			Interest at		Three months
	(unaudited)		March 31,		ended March 31,			March 31,	December 31,
	(millions of dollars)		2015		2015		2014	2015	2014
	Northern Border(a)		50%		20		23	503	505
	Great Lakes		46.45%		11		10	680	672
					31		33	1,183	1,177
		(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.
Northern Border
Investments in unconsolidated affiliates
Summarized financial information for equity investees
	(unaudited)
	(millions of dollars)		March 31, 2015			December 31, 2014
	ASSETS
	Cash and cash equivalents		51			41
	Other current assets		36			34
	Plant, property and equipment, net		1,150			1,163
	Other assets		33			34
			1,270			1,272
	LIABILITIES AND PARTNERS’ EQUITY
	Current liabilities		65			64
	Deferred credits and other		23			22
	Long-term debt, including current maturities		411			411
	Partners’ equity
	Partners’ capital		773			777
	Accumulated other comprehensive loss		(2	)		(2	)
			1,270			1,272
			Three months ended
	(unaudited)		March 31,
	(millions of dollars)		2015			2014
	Transmission revenues		75			86
	Operating expenses		(16	)		(18	)
	Depreciation		(15	)		(15	)
	Financial charges and other		(5	)		(6	)
	Net income		39			47
Great Lakes
Investments in unconsolidated affiliates
Summarized financial information for equity investees
	(unaudited)
	(millions of dollars)		March 31, 2015			December 31, 2014
	ASSETS
	Current assets		88			66
	Plant, property and equipment, net		741			748
			829			814
	LIABILITIES AND PARTNERS’ EQUITY
	Current liabilities		45			38
	Long-term debt, including current maturities		307			316
	Partners’ equity		477			460
			829			814
			Three months ended
	(unaudited)		March 31,
	(millions of dollars)		2015			2014
	Transmission revenues		48			48
	Operating expenses		(11	)		(12	)
	Depreciation		(7	)		(7	)
	Financial charges and other		(6	)		(7	)
	Net income		24			22

CREDIT_FACILITIES_SHORTTERM_LO1

CREDIT FACILITIES, SHORT-TERM LOAN FACILITY AND LONG-TERM DEBT (Tables)	3 Months Ended
	Mar. 31, 2015
CREDIT FACILITIES, SHORT-TERM LOAN FACILITY AND LONG-TERM DEBT
Schedule of credit facilities, short-term loan facility and long-term debt
	(unaudited)
	(millions of dollars)	March 31, 2015	December 31, 2014
	Senior Credit Facility due 2017	320	330
	Term Loan Facility due 2018	500	500
	Short-Term Loan Facility due 2015	170	170
	4.65% Unsecured Senior Notes due 2021, net of discount	350	350
	(2015 and 2014 – nil)
	4.375% Unsecured Senior Notes due 2025, net of $1 million discount	349	-
	5.09% Unsecured Senior Notes due 2015	75	75
	5.29% Unsecured Senior Notes due 2020	100	100
	5.69% Unsecured Senior Notes due 2035	150	150
	3.82% Series D Senior Notes due 2017	20	20
		2,034	1,695
	Less: current portion	249	249
		1,785	1,446
Schedule of principal repayments required on debt
	(unaudited)
	(millions of dollars)
	2015	249
	2016	4
	2017	332
	2018	500
	2019	-
	2020	100
	Thereafter	849
		2,034

NET_INCOME_PER_COMMON_UNIT_Tab

NET INCOME PER COMMON UNIT (Tables)	3 Months Ended
	Mar. 31, 2015
NET INCOME PER COMMON UNIT
Schedule of net income per common unit
			Three months ended
	(unaudited)		March 31,
	(millions of dollars, except per common unit amounts)		2015		2014
	Net income attributable to controlling interests		57		57
	Net income allocated to General Partner, including incentive distribution rights (IDRs) (a)		1		1
	Net income allocable to common units		56		56
	Weighted average common units outstanding (millions) – basic and diluted (b)		63.6		62.3
	Net income per common unit – basic and diluted		$		$
			0.88		0.90
		(a)		In the calculation of basic and diluted net income per common unit, the net income allocated to the General Partner includes IDRs pertaining to the current reporting period, but declared and paid in the subsequent period.
		(b)		Under the ATM program, the Partnership has issued 1,288,481 common units.

CHANGE_IN_OPERATING_WORKING_CA1

CHANGE IN OPERATING WORKING CAPITAL (Tables)	3 Months Ended
	Mar. 31, 2015
CHANGE IN OPERATING WORKING CAPITAL
Summary of change in operating working capital	(unaudited)	Three months ended March 31,
	(millions of dollars)	2015		2014
	Change in accounts receivable and other	(1	)	3
	Change in accounts payable and accrued liabilities	2		4
	Change in accounts payable to affiliates	(7	)	1
	Change in accrued interest	9		8
	Change in operating working capital	3		16

RELATED_PARTY_TRANSACTIONS_Tab

RELATED PARTY TRANSACTIONS (Tables)	3 Months Ended
	Mar. 31, 2015
RELATED PARTY TRANSACTIONS
Summary of capital and operating costs charged to pipeline systems by related party
			Three months ended
	(unaudited)		March 31,
	(millions of dollars)		2015		2014
	Capital and operating costs charged by TransCanada’s subsidiaries to:
	GTN (a)		6		6
	Northern Border (a)		7		7
	Bison (a)		1		1
	Great Lakes (a)		6		7
	North Baja		1		1
	Tuscarora		1		1
	Impact on the Partnership’s net income attributable to controlling interests:
	GTN		4		4
	Northern Border		3		4
	Bison		1		1
	Great Lakes		3		3
	North Baja		1		1
	Tuscarora		1		1
		(a)		Represents 100 percent of the costs.
Summary of amount payable to related party for costs charged
	(unaudited)
	(millions of dollars)		March 31, 2015		December 31, 2014
	Amount payable to TransCanada’s subsidiaries for costs charged in the period by:
	GTN (a)		5		10
	Northern Border (a)		4		10
	Bison		1		2
	Great Lakes (a)		4		9
	North Baja		1		1
	Tuscarora		1		1
		(a)		Represents 100 percent of the costs.

FAIR_VALUE_MEASUREMENTS_Tables

FAIR VALUE MEASUREMENTS (Tables)	3 Months Ended
	Mar. 31, 2015
FAIR VALUE MEASUREMENTS
Schedule of estimated fair value of debt
	(unaudited)	March 31, 2015		December 31, 2014
	(millions of dollars)	Carrying Value	Fair Value	Carrying Value	Fair Value
	Senior Credit Facility due 2017	320	320	330	330
	Term Loan Facility due 2018	500	500	500	500
	Short-Term Loan Facility due 2015	170	170	170	170
	4.65% Senior Notes due 2021, net	350	368	350	375
	4.375% Senior Notes due 2025, net	349	353	-	-
	5.09% Unsecured Senior Notes due 2015	75	76	75	76
	5.29% Unsecured Senior Notes due 2020	100	112	100	111
	5.69% Unsecured Senior Notes due 2035	150	169	150	168
	3.82% Series D Senior Notes due 2017	20	21	20	21
		2,034	2,089	1,695	1,751

ACCOUNTS_RECEIVABLE_AND_OTHER_

ACCOUNTS RECEIVABLE AND OTHER (Tables)	3 Months Ended
	Mar. 31, 2015
ACCOUNTS RECEIVABLE AND OTHER
Schedule of accounts receivable and other	(unaudited)
	(millions of dollars)	March 31, 2015	December 31, 2014
	Trade accounts receivable, net of allowance of nil	30	30
	Accounts receivable from affiliates	1	1
	Other	4	4
		35	35

INVESTMENTS_IN_UNCONSOLIDATED_2

INVESTMENTS IN UNCONSOLIDATED AFFILIATES (Details) (USD $)	1 Months Ended	3 Months Ended
In Millions, unless otherwise specified	Apr. 30, 2006	Mar. 31, 2015	Mar. 31, 2014	Dec. 31, 2014
Investments in unconsolidated affiliates
Equity Earnings from Unconsolidated Affiliates		$31	$33
Investments in Unconsolidated Affiliates		1,183		1,177
Northern Border
Investments in unconsolidated affiliates
Transaction fee	10
Interest acquired by Partnership (as a percent)	20.00%
Great Lakes
Investments in unconsolidated affiliates
Total cash call issued to fund debt repayment		9
Northern Border
Investments in unconsolidated affiliates
Ownership interest (as a percent)		50.00%
Equity Earnings from Unconsolidated Affiliates		20	23
Investments in Unconsolidated Affiliates		503		505
Amortization period of transaction fee	12 years
Undistributed earnings		0	0
Assets
Cash and cash equivalents		51		41
Other current assets		36		34
Plant, property and equipment, net		1,150		1,163
Other assets		33		34
Assets, total		1,270		1,272
LIABILITIES AND PARTNERS' EQUITY
Current liabilities		65		64
Deferred credits and other		23		22
Long-term debt, including current maturities		411		411
Partners' equity
Partners' equity		773		777
Accumulated other comprehensive loss		-2		-2
Liabilities and Partners' Equity, total		1,270		1,272
Revenues (expenses)
Transmission revenues		75	86
Operating expenses		-16	-18
Depreciation		-15	-15
Financial charges and other		-5	-6
Net income		39	47
Great Lakes
Investments in unconsolidated affiliates
Ownership interest (as a percent)		46.45%
Equity Earnings from Unconsolidated Affiliates		11	10
Investments in Unconsolidated Affiliates		680		672
Equity contribution		4	4
Undistributed earnings		0	0
Assets
Current assets		88		66
Plant, property and equipment, net		741		748
Assets, total		829		814
LIABILITIES AND PARTNERS' EQUITY
Current liabilities		45		38
Long-term debt, including current maturities		307		316
Partners' equity
Partners' equity		477		460
Liabilities and Partners' Equity, total		829		814
Revenues (expenses)
Transmission revenues		48	48
Operating expenses		-11	-12
Depreciation		-7	-7
Financial charges and other		-6	-7
Net income		$24	$22

CREDIT_FACILITIES_SHORTTERM_LO2

CREDIT FACILITIES, SHORT-TERM LOAN FACILITY AND LONG-TERM DEBT (Details) (USD $)	3 Months Ended	0 Months Ended			3 Months Ended	0 Months Ended
	Mar. 31, 2015	Apr. 01, 2015	Mar. 31, 2015	Dec. 31, 2014	Mar. 31, 2014	Mar. 13, 2015
Credit facilities, short-term loan facility and long-term debt
Credit facilities, short-term loan facility and long-term debt	$2,034,000,000		2,034,000,000	1,695,000,000
Less: current portion	249,000,000		249,000,000	249,000,000
Long-term debt	1,785,000,000		1,785,000,000	1,446,000,000
Net proceeds	349,000,000
3.82% Series D Senior Notes due 2017
Credit facilities, short-term loan facility and long-term debt
Stated interest rate (as a percent)	3.82%		3.82%	3.82%
Credit facilities, short-term loan facility and long-term debt	20,000,000		20,000,000	20,000,000
Senior Credit Facility, Term Loan Facilities and Short-Term Loan Facility
Credit facilities, short-term loan facility and long-term debt
Leverage ratio (as a percent)		4.97%	5.20%
Senior Credit Facility, Term Loan Facilities and Short-Term Loan Facility | Debt agreement covenants, initial period after occurrence of acquisition
Credit facilities, short-term loan facility and long-term debt
Additional period immediately following the fiscal quarter in which a specified material acquisition occurs	6 months
Senior Credit Facility, Term Loan Facilities and Short-Term Loan Facility | Debt agreement covenants, initial period after occurrence of acquisition | Maximum
Credit facilities, short-term loan facility and long-term debt
Leverage ratio (as a percent)	5.50%
Senior Credit Facility, Term Loan Facilities and Short-Term Loan Facility | Debt agreement covenants, periods subsequent to initial period after occurrence of acquisition | Maximum
Credit facilities, short-term loan facility and long-term debt
Leverage ratio (as a percent)	5.00%
Term loan | Short-Term Loan Facility due 2015
Credit facilities, short-term loan facility and long-term debt
Credit facilities, short-term loan facility and long-term debt	170,000,000		170,000,000	170,000,000
Term loan | Short-Term Loan Facility due 2015 | LIBOR
Credit facilities, short-term loan facility and long-term debt
Variable rate basis	LIBOR
Debt average interest rate (as a percent)	1.30%
Debt interest rate, at period end (as a percent)	1.30%		1.30%
Senior revolving credit facility | Senior Credit Facility due 2017
Credit facilities, short-term loan facility and long-term debt
Credit facilities, short-term loan facility and long-term debt	320,000,000		320,000,000	330,000,000
Maximum borrowing capacity	500,000,000		500,000,000
Amount outstanding under credit facility	320,000,000		320,000,000	330,000,000
Remaining borrowing capacity	180,000,000		180,000,000
Senior revolving credit facility | Senior Credit Facility due 2017 | LIBOR
Credit facilities, short-term loan facility and long-term debt
Variable rate basis	LIBOR			LIBOR	LIBOR
Debt average interest rate (as a percent)	1.43%				1.42%
Debt interest rate, at period end (as a percent)	1.43%		1.43%	1.41%
Term loan | Term Loan Facility due 2018
Credit facilities, short-term loan facility and long-term debt
Credit facilities, short-term loan facility and long-term debt	500,000,000		500,000,000	500,000,000
Term loan | Term Loan Facility due 2018 | LIBOR borrowings | LIBOR
Credit facilities, short-term loan facility and long-term debt
Variable rate basis	LIBOR			LIBOR	LIBOR
Debt average interest rate (as a percent)	1.43%				1.42%
Debt interest rate, at period end (as a percent)	1.43%		1.43%	1.41%
Term loan | Term Loan Facility due 2018 | LIBOR borrowings | LIBOR | Hedges of cash flows | Interest rate swaps
Credit facilities, short-term loan facility and long-term debt
Debt average interest rate (as a percent)	1.83%				1.83%
Unsecured debt | 4.65% Senior Notes due 2021
Credit facilities, short-term loan facility and long-term debt
Stated interest rate (as a percent)	4.65%		4.65%	4.65%
Discount	0		0	0
Credit facilities, short-term loan facility and long-term debt	350,000,000		350,000,000	350,000,000
Unsecured debt | 4.375% Senior Notes due 2025
Credit facilities, short-term loan facility and long-term debt
Stated interest rate (as a percent)	4.38%		4.38%			4.38%
Discount	1,000,000		1,000,000
Credit facilities, short-term loan facility and long-term debt	349,000,000		349,000,000
Amount of debt						350,000,000
Net proceeds						346,000,000
Unsecured debt | 5.09% Senior Notes due 2015
Credit facilities, short-term loan facility and long-term debt
Stated interest rate (as a percent)	5.09%		5.09%	5.09%
Credit facilities, short-term loan facility and long-term debt	75,000,000		75,000,000	75,000,000
Unsecured debt | 5.29% Senior Notes due 2020
Credit facilities, short-term loan facility and long-term debt
Stated interest rate (as a percent)	5.29%		5.29%	5.29%
Credit facilities, short-term loan facility and long-term debt	100,000,000		100,000,000	100,000,000
Unsecured debt | 5.69% Senior Notes due 2035
Credit facilities, short-term loan facility and long-term debt
Stated interest rate (as a percent)	5.69%		5.69%	5.69%
Credit facilities, short-term loan facility and long-term debt	$150,000,000		150,000,000	150,000,000
Subsequent event | GTN | Former parent, TransCanada subsidiaries | Transaction between entities under common control
Credit facilities, short-term loan facility and long-term debt
Interest acquired by Partnership (as a percent)		30.00%
GTN | Unsecured debt | 5.09% Senior Notes due 2015
Credit facilities, short-term loan facility and long-term debt
Stated interest rate (as a percent)	5.09%		5.09%
GTN | Senior Notes | Maximum
Credit facilities, short-term loan facility and long-term debt
Percentage of debt to total capitalization	70.00%

CREDIT_FACILITIES_SHORTTERM_LO3

CREDIT FACILITIES, SHORT-TERM LOAN FACILITY AND LONG-TERM DEBT (Details 2) (USD $)	Mar. 31, 2015	Dec. 31, 2014
In Millions, unless otherwise specified
Principal repayments required on debt
2015	$249
2016	4
2017	332
2018	500
2020	100
Thereafter	849
Total credit facilities and long-term debt	$2,034	$1,695

PARTNERS_EQUITY_Details

PARTNERS' EQUITY (Details) (USD $)	3 Months Ended		1 Months Ended	8 Months Ended
	Mar. 31, 2015	Mar. 31, 2014	Aug. 31, 2014	Mar. 31, 2015
			Institution
TC PipeLines GP, Inc. | General Partner
Partners' Equity
Ownership interest in the Partnership (as a percent)	2.00%	2.00%
ATM Equity Issuance Program | Common Units (Limited Partners)
Partners' Equity
Number of financial institutions			5
Units sold	54,701			1,288,481
Net proceeds from public offering of common units	3,400,000
Sales agent commissions	34,000
ATM Equity Issuance Program | TC PipeLines GP, Inc. | General Partner
Partners' Equity
Equity contribution	100,000
ATM Equity Issuance Program | Maximum | Expected | Common Units (Limited Partners)
Partners' Equity
Gross proceeds from sale of common units			200,000,000
ATM Equity Issuance Program | Minimum | Common Units (Limited Partners)
Partners' Equity
Number of managers to agree with equity sale method			1

NET_INCOME_PER_COMMON_UNIT_Det

NET INCOME PER COMMON UNIT (Details) (USD $)	3 Months Ended
In Millions, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014
General Partner
Partners' Equity
Incentive distributions	$0.30	$0
TC PipeLines GP, Inc. | General Partner
Partners' Equity
General partner interest (as a percent)	2.00%	2.00%

NET_INCOME_PER_COMMON_UNIT_Det1

NET INCOME PER COMMON UNIT (Details 2) (USD $)	3 Months Ended
In Millions, except Per Share data, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014
Net income per common unit
Net income attributable to controlling interests	$57	$57
Net income allocated to General Partner, including incentive distribution rights (IDRs)	1	1
Net income allocable to common units	$56	$56
Weighted average common units outstanding (millions) - basic (in units)	63.6	62.3
Weighted average common units outstanding (millions) - diluted (in units)	63.6	62.3
Net income per common unit - basic (in dollars per unit)	$0.88	$0.90
Net income per common unit - diluted (in dollars per unit)	$0.88	$0.90

NET_INCOME_PER_COMMON_UNIT_Det2

NET INCOME PER COMMON UNIT (Details 3) (ATM Equity Issuance Program, Common Units (Limited Partners))	3 Months Ended	8 Months Ended
	Mar. 31, 2015	Mar. 31, 2015
ATM Equity Issuance Program | Common Units (Limited Partners)
Partners' Equity
Units issued	54,701	1,288,481

CASH_DISTRIBUTIONS_Details

CASH DISTRIBUTIONS (Details) (USD $)	3 Months Ended
In Millions, except Per Share data, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014
Distributions
Partnership distribution (in dollars per unit)	$0.84	$0.81
General Partner
Distributions
Incentive distributions	$0.30	$0
Common units and General Partner interest combined
Distributions
Partnership distribution	$55	$52

CHANGE_IN_OPERATING_WORKING_CA2

CHANGE IN OPERATING WORKING CAPITAL (Details) (USD $)	3 Months Ended
In Millions, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014
CHANGE IN OPERATING WORKING CAPITAL
Change in accounts receivable and other	($1)	$3
Change in accounts payable and accrued liabilities	2	4
Change in accounts payable to affiliates	-7	1
Change in accrued interest	9	8
Change in operating working capital	$3	$16

RELATED_PARTY_TRANSACTIONS_Det

RELATED PARTY TRANSACTIONS (Details) (USD $)	3 Months Ended		0 Months Ended	12 Months Ended
In Millions, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014	Dec. 31, 2014	Dec. 31, 2014
Capital and operating costs charged to the pipeline systems and amount payable
Accounts payable to affiliates	$8		15	$15
Amount included in receivables from related party	1		1	1
General Partner | Reimbursement of costs of services provided
Capital and operating costs charged to the pipeline systems and amount payable
Costs charged	1	1
TransCanada's subsidiaries | GTN
Capital and operating costs charged to the pipeline systems and amount payable
Accounts payable to affiliates	5		10	10
TransCanada's subsidiaries | GTN | Capital and operating costs
Capital and operating costs charged to the pipeline systems and amount payable
Costs charged	6	6
Impact on the Partnership's net income attributable to controlling interests	4	4
Percentage of capital and operating costs charged	100.00%	100.00%	100.00%
TransCanada's subsidiaries | Northern Border
Capital and operating costs charged to the pipeline systems and amount payable
Accounts payable to affiliates	4		10	10
TransCanada's subsidiaries | Northern Border | Capital and operating costs
Capital and operating costs charged to the pipeline systems and amount payable
Costs charged	7	7
Impact on the Partnership's net income attributable to controlling interests	3	4
Percentage of capital and operating costs charged	100.00%	100.00%	100.00%
TransCanada's subsidiaries | Bison
Capital and operating costs charged to the pipeline systems and amount payable
Accounts payable to affiliates	1		2	2
TransCanada's subsidiaries | Bison | Capital and operating costs
Capital and operating costs charged to the pipeline systems and amount payable
Costs charged	1	1
Impact on the Partnership's net income attributable to controlling interests	1	1
Percentage of capital and operating costs charged	100.00%	100.00%
TransCanada's subsidiaries | Great Lakes
Capital and operating costs charged to the pipeline systems and amount payable
Accounts payable to affiliates	4		9	9
Amount included in receivables from related party	11		15	15
TransCanada's subsidiaries | Great Lakes | Capital and operating costs
Capital and operating costs charged to the pipeline systems and amount payable
Costs charged	6	7
Impact on the Partnership's net income attributable to controlling interests	3	3
Percentage of capital and operating costs charged	100.00%	100.00%	100.00%
TransCanada's subsidiaries | Great Lakes | Transportation contracts
Capital and operating costs charged to the pipeline systems and amount payable
Revenues from related party	29	22
TransCanada's subsidiaries | Great Lakes | Transportation contracts | Total revenues | Major customers
Capital and operating costs charged to the pipeline systems and amount payable
Percent of total revenues	61.00%	47.00%
TransCanada's subsidiaries | North Baja Pipeline, LLC
Capital and operating costs charged to the pipeline systems and amount payable
Accounts payable to affiliates	1		1	1
TransCanada's subsidiaries | North Baja Pipeline, LLC | Capital and operating costs
Capital and operating costs charged to the pipeline systems and amount payable
Costs charged	1	1
Impact on the Partnership's net income attributable to controlling interests	1	1
TransCanada's subsidiaries | Tuscarora Gas Transmission Company
Capital and operating costs charged to the pipeline systems and amount payable
Accounts payable to affiliates	1		1	1
TransCanada's subsidiaries | Tuscarora Gas Transmission Company | Capital and operating costs
Capital and operating costs charged to the pipeline systems and amount payable
Costs charged	1	1
Impact on the Partnership's net income attributable to controlling interests	1	1
TransCanada's subsidiaries | Great Lakes
Capital and operating costs charged to the pipeline systems and amount payable
Revenue from TransCanada and its affiliates included in the Partnership's equity earnings	14	11
ANR Pipeline Company | Great Lakes | Firm service between Michigan and Wisconsin
Capital and operating costs charged to the pipeline systems and amount payable
Revenue deferred related to services performed	$14			$9.40

FAIR_VALUE_MEASUREMENTS_Detail

FAIR VALUE MEASUREMENTS (Details) (USD $)	Mar. 31, 2015	Dec. 31, 2014	Mar. 13, 2015
In Millions, unless otherwise specified
3.82% Series D Senior Notes due 2017
Financial Instruments
Stated interest rate (as a percent)	3.82%	3.82%
Unsecured debt | 4.65% Senior Notes due 2021
Financial Instruments
Stated interest rate (as a percent)	4.65%	4.65%
Unsecured debt | 4.375% Senior Notes due 2025
Financial Instruments
Stated interest rate (as a percent)	4.38%		4.38%
Unsecured debt | 5.09% Senior Notes due 2015
Financial Instruments
Stated interest rate (as a percent)	5.09%	5.09%
Unsecured debt | 5.29% Senior Notes due 2020
Financial Instruments
Stated interest rate (as a percent)	5.29%	5.29%
Unsecured debt | 5.69% Senior Notes due 2035
Financial Instruments
Stated interest rate (as a percent)	5.69%	5.69%
Carrying Value
Financial Instruments
Debt	2,034	1,695
Carrying Value | 3.82% Series D Senior Notes due 2017
Financial Instruments
Debt	20	20
Carrying Value | Term loan | Short-Term Loan Facility due 2015
Financial Instruments
Debt	170	170
Carrying Value | Senior revolving credit facility | Senior Credit Facility due 2017
Financial Instruments
Debt	320	330
Carrying Value | Term loan | Term Loan Facility due 2018
Financial Instruments
Debt	500	500
Carrying Value | Unsecured debt | 4.65% Senior Notes due 2021
Financial Instruments
Debt	350	350
Carrying Value | Unsecured debt | 4.375% Senior Notes due 2025
Financial Instruments
Debt	349
Carrying Value | Unsecured debt | 5.09% Senior Notes due 2015
Financial Instruments
Debt	75	75
Carrying Value | Unsecured debt | 5.29% Senior Notes due 2020
Financial Instruments
Debt	100	100
Carrying Value | Unsecured debt | 5.69% Senior Notes due 2035
Financial Instruments
Debt	150	150
Fair Value | Level 2
Financial Instruments
Debt	2,089	1,751
Fair Value | Level 2 | 3.82% Series D Senior Notes due 2017
Financial Instruments
Debt	21	21
Fair Value | Level 2 | Term loan | Short-Term Loan Facility due 2015
Financial Instruments
Debt	170	170
Fair Value | Level 2 | Senior revolving credit facility | Senior Credit Facility due 2017
Financial Instruments
Debt	320	330
Fair Value | Level 2 | Term loan | Term Loan Facility due 2018
Financial Instruments
Debt	500	500
Fair Value | Level 2 | Unsecured debt | 4.65% Senior Notes due 2021
Financial Instruments
Debt	368	375
Fair Value | Level 2 | Unsecured debt | 4.375% Senior Notes due 2025
Financial Instruments
Debt	353
Fair Value | Level 2 | Unsecured debt | 5.09% Senior Notes due 2015
Financial Instruments
Debt	76	76
Fair Value | Level 2 | Unsecured debt | 5.29% Senior Notes due 2020
Financial Instruments
Debt	112	111
Fair Value | Level 2 | Unsecured debt | 5.69% Senior Notes due 2035
Financial Instruments
Debt	169	168

FAIR_VALUE_MEASUREMENTS_Detail1

FAIR VALUE MEASUREMENTS (Details 2) (USD $)	3 Months Ended
In Millions, unless otherwise specified	Mar. 31, 2014	Mar. 31, 2015	Dec. 31, 2014
Interest rate swaps from September 3, 2013 through July 1, 2018 | Term loan | Term Loan Facility due 2018
Interest rate derivatives
Amount of variable-rate debt hedged		$150
Weighted average fixed interest rate (as a percent)		2.79%
Interest rate swaps
Interest rate derivatives
Amount recorded in net income related to ineffectiveness for interest rate hedges	0
Hedges of cash flows | Interest rate swaps
Interest rate derivatives
Change in fair value of interest rate derivative instruments recognized in other comprehensive income		1
Hedges of cash flows | Interest rate swaps | Maximum
Interest rate derivatives
Change in fair value of interest rate derivative instruments recognized in other comprehensive income	1
Hedges of cash flows | Interest rate swaps | Financial charges and other
Interest rate derivatives
Net realized loss related to the interest rate swaps	1	1
Designated as hedge | Interest rate swaps | Recurring fair value measurement | Level 2
Interest rate derivatives
Fair value of derivatives, gross		2	1
Fair value of derivatives, net		$2	$1

ACCOUNTS_RECEIVABLE_AND_OTHER_1

ACCOUNTS RECEIVABLE AND OTHER (Details) (USD $)	Mar. 31, 2015	Dec. 31, 2014
In Millions, unless otherwise specified
ACCOUNTS RECEIVABLE AND OTHER
Trade accounts receivable, net of allowance of nil	$30	$30
Accounts receivable from affiliates	1	1
Other	4	4
Accounts receivable and other	35	35
Trade accounts receivable, allowance	$0	$0

SUBSEQUENT_EVENTS_Details

SUBSEQUENT EVENTS (Details) (Subsequent event, GTN, Former parent, TransCanada subsidiaries, Transaction between entities under common control, USD $)	0 Months Ended
	Apr. 01, 2015	Apr. 01, 2015
Acquisition
Interest acquired (as a percent)	30.00%	30.00%
Purchase price	$446,000,000
Purchase price adjustments	10,000,000
Total cash consideration	263,000,000
Assumption of proportional debt	98,000,000
Partnership interest | Class B units
Acquisition
Equity issuance	95,000,000
Distributions
Portion of GTN's annual distributions to which the Class B units are entitled to receive a percentage share of the distributions above $20 million (as a percent)	30.00%
Period for payment of 30 percent of GTN's distributions above $20 million at 100 percent	5 years
Percentage applied to 30 percent of GTN's distributions above $20 million for the first five years	100.00%
Threshold of 30 percent of GTN's annual distributions for payment to Class B units at specified percentage	$20,000,000
Percentage applied to 30 percent of GTN's distributions above $20 million after the first five years	25.00%

SUBSEQUENT_EVENTS_Details_2

SUBSEQUENT EVENTS (Details 2) (USD $)	0 Months Ended
In Millions, except Per Share data, unless otherwise specified	Apr. 23, 2015	Apr. 21, 2015	Apr. 01, 2015	1-May-15	Mar. 31, 2015
Northern Border
Distributions
Ownership interest (as a percent)					50.00%
Great Lakes
Distributions
Ownership interest (as a percent)					46.45%
Subsequent event
Distributions
Cash distribution (in dollars per unit)	$0.84
Subsequent event | GTN
Distributions
Distribution declared		$37
Ownership interest (as a percent)			100.00%
Subsequent event | Distribution declared | Northern Border
Distributions
Partnership distribution		52
Subsequent event | Distribution declared | Great Lakes
Distributions
Partnership distribution		30
Subsequent event | Cash Distribution Paid | Northern Border
Distributions
Partnership's share of distributions				26
Subsequent event | Cash Distribution Paid | Great Lakes
Distributions
Partnership's share of distributions				$14

SUBSEQUENT_EVENTS_Details_3

SUBSEQUENT EVENTS (Details 3) (Subsequent event, GTN, Expected)	0 Months Ended
	Apr. 23, 2015
Subsequent event | GTN | Expected
Subsequent events
Mainline rate reduction on July 1, 2015	3.00%
Additional rate decrease January 2016 through December 31, 2019	10.00%
Additional rate decrease January 1, 2020 through December 31, 2021	8.00%