NET INCOME PER COMMON UNIT - Terms of Class B Unit Distributions and Determination of Net Income per Common Unit (Details) - USD ($) $ / shares in Units, shares in Millions	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Net income (loss) per common unit
Net income attributable to controlling interests	$ 73,000,000	$ 57,000,000
Net income attributable to the General Partner	(1,000,000)	(1,000,000)
Incentive distributions attributable to the General Partner	(1,000,000)
Class B units
Net income (loss) per common unit
Net income attributable to limited partners	0
Common units
Net income (loss) per common unit
Net income attributable to limited partners	$ 71,000,000	$ 56,000,000
Weighted average common units outstanding - basic (in units)	64.4	63.6
Weighted average common units outstanding - diluted (in units)	64.4	63.6
Net income per common unit - basic (in dollars per unit)	$ 1.10	$ 0.88
Net income per common unit - diluted (in dollars per unit)	$ 1.10	$ 0.88
GTN | Class B units | TransCanada | Distributions
Distributions
Percentage applied to GTN's distributable cash flow for the twelve month period ending December 31, 2016	30.00%
Threshold of GTN's total distributable cash flows for payment to Class B units	$ 20,000,000