NET INCOME PER COMMON UNIT (Details 2) - USD ($) $ / shares in Units, shares in Millions		3 Months Ended		6 Months Ended	9 Months Ended
	Apr. 01, 2015	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2015	Sep. 30, 2014
Net income per common unit
Net income attributable to controlling interests		$ 49,000,000	$ 31,000,000		$ 150,000,000	$ 125,000,000
Net income attributable to the General Partner		(1,000,000)	(1,000,000)		(3,000,000)	(3,000,000)
Incentive distributions attributable to the General Partner		(1,000,000)			(2,000,000)
Class B units
Net income per common unit
Net income allocated to limited partners		2,000,000		$ 2,000,000	2,000,000
Common units
Net income per common unit
Net income allocated to limited partners		$ 45,000,000	$ 30,000,000		$ 143,000,000	$ 122,000,000
Weighted average common units outstanding (millions) - basic (in units)		64.0	62.6		63.8	62.4
Weighted average common units outstanding (millions) - diluted (in units)		64.0	62.6		63.8	62.4
Net income per common unit - basic (in dollars per unit)		$ 0.70	$ 0.48		$ 2.23	$ 1.96
Net income per common unit - diluted (in dollars per unit)		$ 0.70	$ 0.48		$ 2.23	$ 1.96
GTN
Distributions
30% of GTN's distributable cash flow				$ 17,000,000
GTN | Class B units | TransCanada | Distributions
Distributions
Portion of GTN's annual distributions to which the Class B units are entitled to receive a percentage share of the distributions above threshold (as a percent)	30.00%
Percentage applied to GTN's distributable cash flow for the nine months ending December 31, 2015				30.00%
Prorated threshold of GTN's distributions for payment to Class B units				$ 15,000,000