Equity - Additional Information (Detail) - USD ($)		1 Months Ended	3 Months Ended
	Oct. 31, 2016	Aug. 31, 2016	Sep. 30, 2016	Sep. 30, 2015	May 31, 2013
Class of Stock [Line Items]
Aggregate cost of shares repurchased			$ 0	$ 13,000,000
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
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
Class B Common Stock [Member]
Class of Stock [Line Items]
Cash dividend declared		$ 0.10	$ 0.10	$ 0.10