NET INCOME PER COMMON UNIT (Details) (USD $) In Millions, except Per Share data, unless otherwise specified	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013
Ownership interests in the Partnership
Net income	$ 67	$ 53	[1]
Net income attributed to GTN and Bison's former parent		(14)
Net income attributable to non-controlling interests	(10)	(10)	[1]
Net income attributable to controlling interests	57	29	[1]
Net income allocated to General Partner	1	1	[1]
Net income allocable to common units	56	28	[1]
Weighted average common units outstanding (millions) - basic (in units)	62.3	53.5	[1]
Weighted average common units outstanding (millions) - diluted (in units)	62.3	53.5	[1]
Net income per common unit - basic (in dollars per unit)	$ 0.90	$ 0.52	[1]
Net income per common unit - diluted (in dollars per unit)	$ 0.90	$ 0.52	[1]
General Partner
Ownership interests in the Partnership
Net income	$ 1
TC PipeLines GP, Inc. | General Partner
Ownership interests in the Partnership
Additional percentage investment held by General Partner	2.00%

[1] (a) Recast as discussed in Note 2.