Investment in Expedia - Additional Information (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	1 Months Ended	9 Months Ended
	Oct. 31, 2017	Sep. 30, 2017	Feb. 28, 2015
Schedule of Equity Method Investments [Line Items]
Common Stock, Dividends, Per Share, Declared	$ 0.30
Proceeds from Dividends Received		$ 20
Expedia
Schedule of Equity Method Investments [Line Items]
Dividends, Common Stock, Cash		$ 130
Stock Repurchase Program, Number of Shares Authorized to be Repurchased			10.0
Stock Repurchase Program, Remaining Number of Shares Authorized to be Repurchased		6.2
Treasury Stock, Shares, Acquired		1.0
Treasury Stock, Value, Acquired, Cost Method		$ 139