Income Taxes (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012	Dec. 31, 2012
Income tax
Net UTB impacting the effective tax rate	$ 198		$ 185
Period discussed over which uncertain tax positions could include material unrecognized tax benefits due to the closing of various audit years	12 months
Interest and penalties related to unrecognized tax benefits, expense (benefit) recognized on a gross basis	4	(3)
Interest and penalties related to unrecognized tax benefits, accrued on a gross basis	46		44
Deferred tax assets valuation allowance	$ 28		$ 29
Reconciliation of Effective Income Tax Rate
Effective tax rate (as a percent)	29.10%	28.80%
Change in effective income tax rate from prior reporting period to current reporting period (as a percent)	0.30%
Change in effective tax rate from prior reporting period to current reporting period primarily due to reinstatement of research and development tax credit and international taxes	(3.30%)
Change in effective income tax rate from prior reporting period to current reporting period due to adjustments to income tax reserves and other items	3.60%