Stock Compensation Plans - Stock Option Transactions Under Various Stock-Based Employee Compensation Plans (Detail) - $ / shares	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Stock option activity, shares
Outstanding, beginning of year (in shares)	410,900
Granted (in shares)	49,500
Exercised (in shares)	(60,385)	(194,035)	(156,491)
Forfeited (in shares)	(7,200)
Expired (in shares)	(1,800)
Outstanding, end of year (in shares)	391,015	410,900
Weighted-average exercise price per stock option
Outstanding, beginning of year, weighted average exercise price (in usd per share)	$ 83.39
Granted, weighted average exercise price (in usd per share)	87.82
Exercised, weighted average exercise price (in usd per share)	71.21
Forfeited, weighted average exercise price (in usd per share)	84.09
Expired, weighted average exercise price (in usd per share)	84.09
Outstanding, end of year, weighted average exercise price (in usd per share)	$ 85.81	$ 83.39
Exercisable at end of year (in shares)	261,915
Exercisable, at end of year, weighted average exercise price (in usd per share)	$ 80.28
Outstanding, end of year, weighted average remaining contractual term	6 years 4 months 17 days
Exercisable, at end of year, weighted average remaining contractual term	5 years 5 months 4 days