Stockholders' Equity - Additional Information (Detail) - USD ($)	1 Months Ended	12 Months Ended
	Jan. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Jul. 31, 2014	Jan. 31, 2014
Class of Stock [Line Items]
Common stock, shares authorized		110,000,000	110,000,000
Common stock entitles		One
Shares repurchase program authorized					$ 65,000,000	$ 35,000,000
Shares repurchase program expiration date		Feb. 29, 2016
Cash dividends declared per common share		$ 0.80	$ 0.64	$ 0.52
Quarterly dividends payable, date to be paid		Feb. 25, 2016
Quarterly dividends payable, date of record		Feb. 11, 2016
Subsequent Event [Member]
Class of Stock [Line Items]
Shares repurchase program authorized	$ 25,000,000
Cash dividends declared per common share	$ 0.26
Common Stock Non-Voting [Member]
Class of Stock [Line Items]
Common stock, shares authorized		10,000,000	10,000,000
Common Stock Voting [Member]
Class of Stock [Line Items]
Common stock, shares authorized		110,000,000