Equity - Additional Information (Detail) - USD ($)		1 Months Ended		6 Months Ended
	Nov. 01, 2019	Aug. 31, 2019	Aug. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	May 31, 2013
Class of Stock [Line Items]
Cash dividends per common share, date of dividend payable		Oct. 16, 2019	Oct. 17, 2018
Cash dividends per common share, date of record for dividend		Sep. 11, 2019	Sep. 12, 2018
Class A Common Stock [Member]
Class of Stock [Line Items]
Number of shares repurchased	5,200,000
Remaining authorized amount under stock repurchase program	$ 429,000,000
Aggregate amount of shares authorized to be repurchased						$ 500,000,000
Aggregate cost of shares repurchased	$ 71,000,000
Shares Repurchased During period				0	0
Cash dividends declared per share of common stock		$ 0.10	$ 0.10
Class B Common Stock [Member]
Class of Stock [Line Items]
Shares Repurchased During period				0	0
Cash dividends declared per share of common stock		$ 0.10	$ 0.10