Stock Plans - Summary of Performance Stock Unit Activity (Detail) - Performance stock - $ / shares	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Shares
Beginning balance (in shares)	200,212	238,035	218,886
Granted (in shares)	52,309	67,479	83,819
Vested (in shares)	(64,543)	(132,036)	(139,478)
Performance adjustments (in shares)	5,357	33,499	76,960
Forfeited (in shares)		(6,765)	(2,152)
Ending balance (in shares)	193,335	200,212	238,035
Weighted Average Exercise Price
Beginning balance (in dollars per share)	$ 104.69	$ 85.39	$ 68.43
Granted (in dollars per share)	175.59	127.48	101.03
Vested (in dollars per share)	85.41	73.00	44.75
Performance adjustments (in dollars per share)	88.45	72.36	44.24
Forfeited (in dollars per share)		111.60	99.82
Ending balance (in dollars per share)	$ 129.86	$ 104.69	$ 85.39