Income Taxes (Details 3) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014	Dec. 31, 2014
Reconciliation of Effective Income Tax Rate
Effective tax rate (as a percent)	28.10%	29.50%	28.80%	28.50%
Income tax
Net UTB impacting the effective tax rate	$ 232		$ 232		$ 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	$ (4)	$ 2	(2)	$ (13)
Interest and penalties related to unrecognized tax benefits, accrued on a gross basis	$ 41		$ 41		44
Change in effective income tax rate from prior reporting period to current reporting period (as a percent)	(1.40%)		0.30%
Impact of factors that decreased the effective tax rate from prior reporting period to current reporting period (as a percent)	(3.70%)		(2.20%)
Impact of factors that increased the effective tax rate from prior reporting period to current reporting period (as a percent)	2.30%		2.50%
Deferred tax assets valuation allowance	$ 22		$ 22		$ 22