CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (Parenthetical) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Unrealized gain (loss) on derivative instruments, income tax expense (benefit)	$ 1	$ (2)	$ 0	$ 0
Reclassification of (gain) loss on settled derivative instruments, income tax expense (benefit)	0	(6)	7	(7)
Unrealized gain (loss) on investments, income tax expense (benefit)	0	(6)	(3)	(2)
Reclassification of impairment of investment, income tax expense (benefit)	$ 0	$ 0	$ 4	$ 0