CONSOLIDATED STATEMENTS OF INCOME - USD ($) shares in Millions, $ in Millions	3 Months Ended		6 Months Ended	9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2015	Sep. 30, 2014
Transmission revenues	$ 83	$ 80		$ 255	$ 249
Equity earnings from unconsolidated affiliates (Note 4)	17	15		63	66
Operation and maintenance expenses	(12)	(14)		(36)	(38)
Property taxes	(5)	(5)		(16)	(17)
General and administrative	(1)	(5)		(5)	(8)
Depreciation	(21)	(21)		(63)	(64)
Financial charges and other (Note 14)	(12)	(11)		(41)	(37)
Net income	49	39		157	151
Net income attributable to non-controlling interests		8		7	26
Net income attributable to controlling interests	49	31		150	125
Calculation of net income attributable to common units
Net income attributable to controlling interests	49	31		150	125
Net income allocated to the General Partner, including incentive distributions	2	1		5	3
Class B units
Calculation of net income attributable to common units
Net income attributable to limited partners (Note 8)	2		$ 2	2
Common units
Calculation of net income attributable to common units
Net income attributable to limited partners (Note 8)	$ 45	$ 30		$ 143	$ 122
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 (Note 8) - basic (in dollars per unit)	$ 0.70	$ 0.48		$ 2.23	$ 1.96
Net income per common unit (Note 8) - diluted (in dollars per unit)	$ 0.70	$ 0.48		$ 2.23	$ 1.96
Common units outstanding, end of period (millions) (in units)	64.0	63.6	64.0	64.0	63.6