CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (Parenthetical) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Unrealized gain on derivative instruments, net of income tax expense of $0, $1 and $4	$ 0	$ 1	$ 4
Reclassification of (gain) loss on settled derivative instruments, net of income tax expense (benefit) of $12 million, ($10) million and ($139) million	14	12	(10)
Unrealized loss on investments, net of income tax benefit of $0, ($4) and ($4)	0	(4)	(4)
Reclassification of (gain) loss on investment, net of income tax expense (benefit) of $3 million, $0 and $0	$ (3)	$ 3	$ 0