Consolidated Statements of Operations (Parenthetical) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Statement [Abstract]
Income from operations of discontinued businesses, income tax expense (benefit)	$ (21)	$ 229	$ (53)
Gain (loss) from disposal and impairment of discontinued businesses, income tax expense (benefit)	$ 0	$ 266	$ 0