Income Taxes (Details 3) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014	Dec. 31, 2014
Reconciliation of Effective Income Tax Rate
Effective tax rate (as a percent)	29.50%	27.40%
Income tax
Net UTB impacting the effective tax rate	$ 268		$ 265
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	2	(15)
Interest and penalties related to unrecognized tax benefits, accrued on a gross basis	46		44
Change in effective income tax rate from prior reporting period to current reporting period (as a percent)	2.10%
Impact of factors that increased the effective tax rate from prior reporting period to current reporting period (as a percent)	2.10%
Deferred tax assets valuation allowance	$ 22		$ 22