Income Taxes (Narrative) (Details) (USD $)
In Millions, unless otherwise specified
3 Months Ended
Mar. 31, 2015
Income Tax Disclosure [Abstract]  
Change in income tax expense $ (69)
Change in effective income tax rate (2.80%)
Period within which resolution of tax appeal is reasonably possible (in months) 12 months
Minimum reasonably possible reduction in the amount of unrecognized tax benefits 100
Maximum reasonably possible reduction in the amount of unrecognized tax benefits $ 350