Income Tax (Income Loss from Continuing Operations Before Income Tax Expense from Domestic and Foreign Operations) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income (loss) from continuing operations:
Domestic	$ 684	$ 185	$ 1,874
Foreign	2,852	4,096	3,777
Income (loss) from continuing operations before provision for income tax	$ 3,536	$ 4,281	$ 5,651