CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (Parenthetical) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Unrealized gain on derivative instruments, net of income tax expense of $1 million, $1 million, $1 million and $1 million	$ 1	$ 1	$ 1	$ 1
Reclassification of (gain) loss on settled derivative instruments, net of income tax expense (benefit) of $1 million, ($3) million, $8 million and ($10) million	1	(3)	8	(10)
Unrealized loss on investments, net of income tax benefit of ($1) million, ($2) million, ($4) million and ($4) million	(1)	(2)	(4)	(4)
Reclassification of (gain) loss on investment, net of income tax expense (benefit) of ($1) million, $0, $3 million and $0	$ (1)	$ 0	$ 3	$ 0