Income Taxes (Details 3) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013	Dec. 31, 2013
Reconciliation of Effective Income Tax Rate
Effective tax rate (as a percent)	27.40%	29.10%
Income tax
Net UTB impacting the effective tax rate	$ 192		$ 262
Period discussed over which the Company is not able to reasonably estimate the amount by which the liability for unrecognized tax benefits could change as a result of ongoing income tax authority examinations	12 months
Interest and penalties related to unrecognized tax benefits, expense (benefit) recognized on a gross basis	(15)	4
Interest and penalties related to unrecognized tax benefits, accrued on a gross basis	43		62
Change in effective income tax rate from prior reporting period to current reporting period (as a percent)	(1.70%)
Impact of factors that decreased the effective tax rate from prior reporting period to current reporting period (as a percent)	(3.40%)
Impact of factors that increased the effective tax rate from prior reporting period to current reporting period (as a percent)	1.70%
Deferred tax assets valuation allowance	$ 24		$ 23