Income Taxes (Schedule of Income Tax Provision (Benefit)) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Current Income Tax Expense (Benefit), Continuing Operations [Abstract]
US	$ 201	$ (22)	$ 28
International	158	60	152
Total	359	38	180
Deferred Income Tax Expense (Benefit), Continuing Operations [Abstract]
US	(110)	108	54
International	(36)	(24)	(33)
Total	(146)	84	21
Income tax provision (benefit)	$ 213	$ 122	$ 201