Income Taxes (Details 4) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Reconciliation of our uncertain tax positions
Balance January 1	$ 111	$ 96	$ 83
Gross increases in tax positions in current period	19	23	17
Gross increases in tax positions in prior period	3	4	16
Gross decreases in tax positions in prior period	(10)	(6)
Gross decreases settlements		(2)	(17)
Gross decreases statute of limitations expired	(4)	(4)	(3)
Balance December 31	$ 119	$ 111	$ 96