NET INCOME (LOSS) PER COMMON UNIT - Determination and Terms of Class B Unit Distributions (Details 2) - USD ($) $ / shares in Units, shares in Millions		3 Months Ended								9 Months Ended	12 Months Ended
	Apr. 01, 2015	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Net income (loss) per common unit
Net income attributable to controlling interests		$ (137,000,000)	$ 49,000,000	$ 44,000,000	$ 57,000,000	$ 47,000,000	$ 31,000,000	$ 37,000,000	$ 57,000,000		$ 13,000,000	$ 172,000,000	$ 155,000,000	[1]
Net income attributed to GTN and Bison's former parent													(26,000,000)
Net income allocable to General and Limited Partners											13,000,000	172,000,000	129,000,000
Incentive distributions attributable to the General Partner											(3,000,000)	(1,000,000)
Net income (loss) allocable to the General Partner and common units											$ (2,000,000)	171,000,000	129,000,000
Net Income (loss) allocable to the General Partner's two percent interest												3,000,000	3,000,000
Distributions
Priority income allocation for incentive distributions allocated to General Partner (as a percent)											100.00%
Class B units
Net income (loss) per common unit
Net income (loss) attributable to limited partners											$ 12,000,000
Common units
Net income (loss) per common unit
Net income (loss) attributable to limited partners											$ (2,000,000)	$ 168,000,000	$ 126,000,000	[1]
Weighted average common units outstanding - basic (in units)											63.9	62.7	58.9	[1]
Weighted average common units outstanding - diluted (in units)											63.9	62.7	58.9
Net income per common unit - basic (in dollars per unit)		$ (2.24)	$ 0.70	$ 0.66	$ 0.88	$ 0.71	$ 0.48	$ 0.58	$ 0.90		$ (0.03)	$ 2.67	$ 2.13	[1]
Net income per common unit - diluted (in dollars per unit)											$ (0.03)	$ 2.67	$ 2.13
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
30% of GTN's distributable cash flow										$ 27,000,000

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