Fair Value Fair Value (Details 2) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Fair Value, Inputs, Level 2 [Member]
Fair Value Transfers Between Level 1, Level 2 and Level 3 [Line Items]
Transfers into Level 1	$ 0	$ 0	$ 0	$ 0
Transfers into Level 3	0	(7)	29	(4)
Fair Value, Inputs, Level 3 [Member]
Fair Value Transfers Between Level 1, Level 2 and Level 3 [Line Items]
Transfers into Level 1	0	0	0	0
Transfers into Level 2	0	42	2	24
Fair Value, Inputs, Level 1 [Member]
Fair Value Transfers Between Level 1, Level 2 and Level 3 [Line Items]
Transfers into Level 2	0	0	0	0
Transfers into Level 3	$ 0	$ 0	$ 0	$ 0