Stock-Based Compensation - Summary of Options Including Non-Plan Stock Options (Detail) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Stock Options:
Outstanding at beginning of year (in shares)	430,736
Granted (in shares)	150,326
Exercised (in shares)	(115,819)
Forfeited (in shares)	(15,482)
Outstanding at end of year (in shares)	449,761	430,736
Nonvested at end of year (in shares)	242,158	140,076
Exercisable at end of year (in shares)	207,603
Weighted- Average Exercise Price
Outstanding at beginning of year (in dollars per share)	$ 34.33
Granted (in dollars per share)	34.93
Exercised (in dollars per share)	24.79
Forfeited (in dollars per share)	39.84
Outstanding at end of year (in dollars per share)	36.80	$ 34.33
Nonvested at end of year (in dollars per share)	38.66	$ 43.91
Exercisable at end of year (in dollars per share)	$ 34.62
Weighted-Average Remaining Contractual Term (Years)
Outstanding at end of year	4 years 1 month 28 days	3 years 1 month 28 days
Nonvested at end of year	2 years 8 months 12 days
Exercisable at end of year	2 years 3 months 18 days
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Intrinsic Value [Roll Forward]
Outstanding at end of year	$ 3,910	$ 4,550
Nonvested at end of year	1,507
Exercisable at end of year	$ 2,313