Consolidated Statements of Stockholders' Equity (Parenthetical) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Statement of Stockholders' Equity [Abstract]
Net Income (Loss) Attributable to Redeemable Noncontrolling Interest	$ 5	$ 5	$ 5
Cash dividends declared (USD per share)	$ 2.54	$ 2.35	$ 2.17