CONSOLIDATED STATEMENT OF COMPREHENSIVE INCOME (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012		Dec. 31, 2011		Dec. 31, 2010
CONSOLIDATED STATEMENT OF COMPREHENSIVE INCOME
Net income	$ 137	[1]	$ 157	[1]	$ 137	[1]
Other comprehensive income
Change associated with current period hedging transactions (Note 15)			14		10
Change associated with current period hedging transaction of investees					1
Total other comprehensive income			14		11
Total comprehensive income	$ 137		$ 171		$ 148

[1] 25 percent interests in each of GTN and Bison were acquired in May 2011.