Income Taxes (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2012	Mar. 31, 2011	Dec. 31, 2011
Reconciliation of Effective Income Tax Rate
Effective tax rate (as a percent)	28.80%	28.60%
Income tax
Net UTB impacting the effective tax rate	$ 246		$ 295
Period discussed over which uncertain tax positions could include material unrecognized tax benefits due to the closing of various audit years (in months)	P12M
Interest and penalties related to unrecognized tax benefits, expense (benefit) recognized on a gross basis	(3)	(2)
Interest and penalties related to unrecognized tax benefits, accrued on a gross basis	56		56
Change in effective income tax rate from prior reporting period to current reporting period (as a percent)	0.20%
Deferred tax assets valuation allowance	$ 30		$ 82