Income Taxes (Details 3) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Changes in unrecognized tax benefits
Unrecognized tax benefits at beginning of year	$ 296	$ 199	$ 146
Tax positions from current periods	46	62	53
Tax positions increase from prior periods	1	62	12
Tax positions decrease from prior periods	(111)	(27)	(10)
Reductions due to settlements	(112)
Reductions due to expired statute of limitations			(2)
Balance at end of year	$ 120	$ 296	$ 199