Stock Option Plan and Restricted Stock Plan - Schedule of Analysis of Stock Option Activity (Detail)	3 Months Ended
	Mar. 31, 2021 $ / shares shares
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Outstanding, beginning of year, Shares | shares	1,833,057
Exercised, Shares | shares	(124,524)
Cancelled, Shares | shares	(14,100)
Outstanding, end of year, Shares | shares	1,694,433
Exercisable at end of year, Shares | shares	764,953
Outstanding, beginning of year, Weighted-Average Ex. Price | $ / shares	$ 20.85
Exercised, Weighted-Average Ex. Price | $ / shares	16.35
Cancelled, Weighted-Average Ex. Price | $ / shares	24.60
Outstanding, end of year, Weighted-Average Ex. Price | $ / shares	21.15
Exercisable at end of year, Weighted-Average Ex. Price | $ / shares	$ 17.36