Stockholders' Equity - Summary of the Companys Change in the Common Stock (Detail) - shares	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Class of Stock [Line Items]
Outstanding shares of voting common stock at the beginning of year	37,935,984
Exercise of stock options	176,901	106,899	120,588
Outstanding shares of voting common stock at the end of year	38,005,330	37,935,984
Voting Common Stock [Member]
Class of Stock [Line Items]
Outstanding shares of voting common stock at the beginning of year	37,936,000	37,640,000	37,621,000
Exercise of stock options	177,000	147,000	121,000
Issuance of restricted stock, net of cancellations	56,000	161,000	67,000
Shares withheld for withholding tax payments	(125,000)	(98,000)	(45,000)
Treasury shares used for acquisition		146,000
Repurchases	(39,000)	(60,000)	(124,000)
Outstanding shares of voting common stock at the end of year	38,005,000	37,936,000	37,640,000