Income Taxes Income Taxes (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Income Tax Contingency [Line Items]
Effective income tax rate	12.20%	17.50%	16.80%	18.30%
Decrease in uncertain tax positions			$ 10
Amount of liability for uncertain tax positions that would impact the effective tax rate if recognized	$ 144		144
Other Noncurrent Liabilities [Member]
Income Tax Contingency [Line Items]
Liability for uncertain tax positions, noncurrent	197		197
Liability for uncertain tax positions, interest	28		28
Liability for uncertain tax positions, penalties	$ 12		$ 12