Income Taxes (Source of Income (Loss) Before Income Taxes) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Sources of Income (Loss) Before Income Taxes
Income from continuing operations before income taxes	$ 1,568	$ 1,979	$ 1,221
Income (loss) from discontinued operations before income taxes	15	(525)	0
Income before income tax	$ 1,583	$ 1,454	$ 1,221