Income Taxes Income Taxes (Income Tax Expense) (Details) - USD ($) $ in Millions	3 Months Ended			9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Jun. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Income Tax Disclosure [Abstract]
Income Tax Expense (Benefit)	$ 115	$ 130		$ 350	$ 336
Other Tax Expense (Benefit)			$ 175