Income Taxes (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013
Income Tax Disclosure [Line Items]
Income Tax Adjustments, Settlements, and Unusual Provisions		$ 16
Unrecognized Tax Benefits, Decrease Resulting from Prior Period Tax Positions	12
Income tax expense (benefit)	$ 4	$ 2