Stockholders' Equity - Additional Information (Detail)	3 Months Ended	9 Months Ended	12 Months Ended
	Sep. 30, 2016 USD ($) shares	Sep. 30, 2016 USD ($) vote / shares shares	Dec. 31, 2015 USD ($) shares
Class of Stock [Line Items]
Description of voting		Holders of Class A Common Stock and Class B Common Stock are entitled to one vote for each share held on all matters submitted to stockholders for their vote or approval.
Repurchase of common stock		$ 28,543,000
Common Class A [Member]
Class of Stock [Line Items]
Voting rights per share | vote / shares		1
Authorized amount for Stock Repurchase Program	$ 100,000,000	$ 100,000,000
Common Class B [Member]
Class of Stock [Line Items]
Voting rights per share | vote / shares		1
Common Stock [Member] | Common Class A [Member]
Class of Stock [Line Items]
Repurchase of common stock (in shares) | shares	247,366	1,918,999	934,434
Repurchase of common stock	$ 3,800,000	$ 28,500,000	$ 15,000,000