Income Taxes - Income Tax Expense (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Current taxes
Total taxes, current	$ 375	$ 329	$ 683	$ 639
Deferred taxes (benefits)
Total taxes, deferred	(23)	0	(8)	14
Total taxes	$ 352	$ 329	$ 675	$ 653