NET INCOME PER COMMON UNIT (Details) (USD $) In Millions, except Per Share data, unless otherwise specified	3 Months Ended								12 Months Ended												0 Months Ended		12 Months Ended
	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2013		Dec. 31, 2012		Dec. 31, 2011		Dec. 31, 2013 General Partner		Dec. 31, 2012 General Partner		Dec. 31, 2011 General Partner		May 22, 2013 TC PipeLines GP, Inc. General Partner	May 03, 2011 TC PipeLines GP, Inc. General Partner	Dec. 31, 2013 TC PipeLines GP, Inc. General Partner
Ownership interests in the Partnership
Additional percentage investment held by General Partner																					2.00%	2.00%	2.00%
Net income	$ 50	$ 46	$ 42	$ 53	$ 53	$ 57	$ 54	$ 65	$ 191	[1]	$ 229	[1]	$ 250	[1]	$ 3	[1]	$ 4	[1]	$ 4	[1]
Net income attributed to GTN and Bison's former parent									(26)		(55)		(59)				(1)	[1]	(1)	[1]
Net income attributable to non-controlling interests									(36)	[1]	(37)	[1]	(34)	[1]
Net income attributable to controlling interests	41	37	34	43	44	48	46	54	155	[1]	192	[1]	216	[1]
Net income allocated to General Partner									3	[1]	3	[1]	3	[1]
Net income allocable to common units									$ 126	[1]	$ 134	[1]	$ 154	[1]
Weighted average common units outstanding (millions) - basic (in units)									58.9		53.5		51.1
Weighted average common units outstanding (millions) - diluted (in units)									58.9		53.5		51.1
Net income per common unit - basic (in dollars per unit)	$ 0.63	$ 0.58	$ 0.40	$ 0.52	$ 0.56	$ 0.64	$ 0.60	$ 0.71	$ 2.13	[1]	$ 2.51	[1]	$ 3.02	[1]
Net income per common unit - diluted (in dollars per unit)									$ 2.13	[1]	$ 2.51	[1]	$ 3.02	[1]

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