CONSOLIDATED STATEMENTS OF INCOME shares in Millions, $ in Millions	12 Months Ended
	Dec. 31, 2015 USD ($) $ / shares shares	Dec. 31, 2014 USD ($) $ / shares shares	Dec. 31, 2013 USD ($) $ / shares shares
Transmission revenues	$ 344	$ 336	$ 341	[1]
Equity earnings from unconsolidated affiliates (Note 4)	97	88	67	[1]
Impairment of equity-method investment (Note 4)	(199)
Operation and maintenance expenses	(53)	(54)	(55)	[1]
Property taxes	(19)	(21)	(23)	[1]
General and administrative	(9)	(9)	(9)	[1]
Depreciation	(85)	(86)	(86)	[1]
Financial charges and other (Note 11)	(56)	(50)	(44)	[1]
Net income	20	204	191	[1]
Net income attributable to non-controlling interests	7	32	36	[1]
Net income attributable to controlling interests	13	172	155	[1]
Net income (loss) attributable to controlling interest allocation (Note 12)
General Partner	3	4	3	[1]
TransCanada and its subsidiaries	12		26	[1]
Net income attributable to controlling interests	13	172	155	[1]
Common units
Net income (loss) attributable to controlling interest allocation (Note 12)
Limited partners	$ (2)	$ 168	$ 126	[1]
Net income per common unit (Note 12) - basic (in dollars per unit) | $ / shares	$ (0.03)	$ 2.67	$ 2.13	[1]
Net income per common unit (Note 12) - diluted (in dollars per unit) | $ / shares	$ (0.03)	$ 2.67	$ 2.13
Weighted average common units outstanding - basic (in units) | shares	63.9	62.7	58.9	[1]
Weighted average common units outstanding - diluted (in units) | shares	63.9	62.7	58.9
Common units outstanding, end of year (in units) | shares	64.3	63.6	62.3	[1]

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