Equity - Additional Information (Detail) - USD ($)		1 Months Ended		6 Months Ended		21 Months Ended
	Feb. 03, 2017	Feb. 28, 2017	Aug. 31, 2016	Dec. 31, 2016	Dec. 31, 2015	Feb. 03, 2017	May 31, 2013
Class of Stock [Line Items]
Aggregate cost of shares repurchased				$ 0	$ 16,000,000
Dividend declaration date				2016-08
Dividend payable date				Oct. 19, 2016
Dividend record date				Sep. 14, 2016
Subsequent Event [Member]
Class of Stock [Line Items]
Remaining authorized amount under stock repurchase program	$ 429,000,000					$ 429,000,000
Dividend declaration date		2017-02
Dividend payable date		Apr. 19, 2017
Dividend record date		Mar. 15, 2017
Class A Common Stock [Member]
Class of Stock [Line Items]
Aggregate amount of shares authorized to be repurchased							$ 500,000,000
Number of shares repurchased				0
Cash dividend declared			$ 0.10	$ 0.10	$ 0.10
Class A Common Stock [Member] | Subsequent Event [Member]
Class of Stock [Line Items]
Number of shares repurchased						5,200,000
Aggregate cost of shares repurchased	$ 71,000,000
Cash dividend declared		$ 0.10
Class B Common Stock [Member]
Class of Stock [Line Items]
Cash dividend declared			$ 0.10	$ 0.10	$ 0.10
Class B Common Stock [Member] | Subsequent Event [Member]
Class of Stock [Line Items]
Cash dividend declared		$ 0.10