Income Taxes (Source of Income (Loss) Before Income Taxes) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Income Tax Disclosure [Abstract]
Income from continuing operations before income taxes	$ 1,590	$ 1,568	$ 1,979
Income (loss) from discontinued operations before income taxes	1	15	(525)
Income before income tax	$ 1,591	$ 1,583	$ 1,454