Stock Plans - Summary of Stock Option Activity (Detail) - $ / shares	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Shares
Beginning balance, outstanding (in shares)	283,998	559,656	735,001
Granted (in shares)			23,285
Exercised (in shares)	(122,087)	(274,704)	(198,535)
Forfeited (in shares)	(210)	(954)	(95)
Ending balance, outstanding (in shares)	161,701	283,998	559,656
Weighted Average Exercise Price
Beginning, weighted average exercise price (in dollars per share)	$ 46.23	$ 45.78	$ 43.79
Granted (in dollars per share)			43.54
Exercised (in dollars per share)	47.25	45.31	38.16
Forfeited (in dollars per share)	43.75	42.00	49.19
Ending, weighted average exercise price (in dollars per share)	$ 45.47	$ 46.23	$ 45.78
Exercisable at year-end (in shares)	161,347	281,593	552,682