Stockholders' Equity - Summary of the Companys Change in the Common Stock (Detail) - shares	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Class of Stock [Line Items]
Outstanding shares of voting common stock at the beginning of year	37,318,722
Exercise of stock options	196,034	165,340	256,622
Outstanding shares of voting common stock at the end of year	37,409,274	37,318,722
Voting Common Stock [Member]
Class of Stock [Line Items]
Outstanding shares of voting common stock at the beginning of year	37,319,000	37,729,000	37,407,000
Exercise of stock options	183,000	120,000	256,000
Issuance of restricted stock, net of shares withheld for tax payments and cancellations	178,000	116,000	66,000
Repurchases	(271,000)	(646,000)
Outstanding shares of voting common stock at the end of year	37,409,000	37,319,000	37,729,000