Income Taxes (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Income Tax Contingency [Line Items]
Effective income tax rate	14.00%	19.10%	15.80%	18.50%
Increase in uncertain tax positions			$ 7
Amount of liability for uncertain tax positions that would impact the effective tax rate if recognized	$ 161		161
Other Noncurrent Liabilities [Member]
Income Tax Contingency [Line Items]
Liability for uncertain tax positions, noncurrent	208		208
Liability for uncertain tax positions, interest	30		30
Liability for uncertain tax positions, penalties	$ 21		$ 21