Stockholders' Equity (Details) $ in Millions	12 Months Ended
	Dec. 31, 2018 USD ($) vote shares	Dec. 31, 2017 USD ($) shares	Dec. 31, 2016 USD ($) shares	Aug. 31, 2018 USD ($)	Nov. 20, 2015 USD ($)	Nov. 30, 2014 USD ($)
Class of Stock [Line Items]
Dividends, Common Stock, Cash	$ 120	$ 103	$ 97
Common Stock, Voting Rights, Number of Votes Per Share | vote	1
Common stock, sinking fund	$ 0
Stock repurchase program, authorized amount				$ 150	$ 150	$ 250
Stock Repurchase Program, Shares Repurchased, Gross | shares	5,562,479
Treasury Stock Purchase Price, Repurchase Program	$ 335
Ordinary Dividend [Member]
Class of Stock [Line Items]
Dividends, Common Stock, Cash	$ 120	$ 103	$ 97
Treasury Stock [Member]
Class of Stock [Line Items]
Stock repurchased 2014 program, shares repurchase | shares	1,368,881	0	1,511,109