CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2015	Dec. 31, 2014		Dec. 31, 2013
Cash Generated From Operations
Net income		$ 20	$ 204		$ 191	[1]
Depreciation		85	86		86	[1]
Impairment of equity - method investment (Note 4)		199
Amortization of debt issue costs (Note 11)		1	1		1	[1]
Accruals for costs related to acquisition of 49.9% interest in PNGTS (Note 22)		2
Equity earnings in excess of cumulative distributions		(3)
Equity allowance for funds used during construction		(1)
Change in other long-term liabilities	[1]				2
Change in operating working capital (Note 14)		(9)	17		(8)	[1]
Total cash generated from operations		294	308		272	[1]
Investing Activities
Acquisition of interests in GTN and Bison, net of cash acquired (Note 6)			(25)		(921)	[1]
Adjustment to the 2011 Acquisition	[1]				1
Capital expenditures		(54)	(10)		(15)	[1]
Change in affiliate demand loan receivable	[1]				21
Other		1
Total investing activities		(301)	(234)		(920)	[1]
Financing Activities
Distributions paid (Note 13)		(228)	(212)		(188)	[1]
Distributions paid to non-controlling interests		(9)	(50)		(52)	[1]
Change in affiliate demand loan payable	[1]				(15)
Equity contribution by the General Partner (Note 6)		2
Long-term debt issued, net of discount (Note 7)		618	35		937	[1]
Short-term loan issued (Note 7)			170
Long-term debt repaid (Note 7)		(404)	(89)		(372)	[1]
Debt issuance costs		(3)			(2)	[1]
Equity contribution from Bison's former parent (Note 16)	[1]				18
Distributions paid to former parent of GTN and Bison	[1]				(37)
Total financing activities		20	(73)		670	[1]
Increase/(decrease) in cash and cash equivalents		13	1		22	[1]
Cash and cash equivalents, beginning of year		26	25	[1]	3	[1]
Cash and cash equivalents, end of year		39	26		25	[1]
Interest payments made		54	47		42	[1]
Supplemental information about non-cash investing and financing activities
Accrual for Carty Lateral consideration payment (Note 6)	[1]				25
Accrual for costs related to construction of Carty Lateral (Note 14)		10
Issuance of Class B units to TransCanada (Note 6)		95
ATM Equity Issuance Program
Financing Activities
Equity issuance, net (Note 9)		44	73
Equity Issuance, May 2013
Financing Activities
Equity issuance, net (Note 9)	[1]				381
GTN
Investing Activities
Acquisition of the remaining 30 percent interest (Note 6)		(264)
Bison
Investing Activities
Acquisition of the remaining 30 percent interest (Note 6)			(217)
Northern Border
Investing Activities
Cumulative distributions in excess of equity earnings		25	18		20	[1]
Investment in Great Lakes / Northern Border (Note 4)	[1]				(31)
Great Lakes
Investing Activities
Cumulative distributions in excess of equity earnings			9		14	[1]
Investment in Great Lakes / Northern Border (Note 4)		$ (9)	$ (9)		$ (9)	[1]

[1] Recast as discussed in Note 2 and Note 6.