Treasury Stock - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Equity, Class of Treasury Stock [Line Items]
Treasury stock, shares	6,405,000	6,405,000
Treasury stock, cost	$ 475,184,000	$ 475,184,000
Class A | Two Thousand Five Share Repurchase Program
Equity, Class of Treasury Stock [Line Items]
Shares repurchased program expiration date	Apr. 29, 2018
Stock authorized to repurchase by board of directors	$ 800,000,000
Treasury stock, shares	3,826,947
Shares repurchased, average price per share	$ 90.23
Treasury stock, cost	$ 345,300,000