Stock compensation plans- Summary of stock option activity (Detail) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2023 USD ($) $ / shares shares
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Number of options, outstanding, beginning of year (in shares) | shares	1,228,848
Number of options, granted (in shares) | shares	189,388
Number of options, exercised (in shares) | shares	(99,799)
Number of options, forfeited or expired (in shares) | shares	(24,662)
Number of options, outstanding, ending of year (in shares) | shares	1,293,775
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price [Roll Forward]
Weighted average exercise price, outstanding, beginning of year (in dollars per share) | $ / shares	$ 230.58
Weighted average exercise price, granted (in dollars per share) | $ / shares	238.92
Weighted average exercise price, exercised (in dollars per share) | $ / shares	108.19
Weighted average exercise price, forfeited or expired (in dollars per share) | $ / shares	319.20
Weighted average exercise price, outstanding, beginning of year (in dollars per share) | $ / shares	$ 239.55
Share-based Compensation Arrangement by Share-based Payment Award, Options, Additional Disclosures [Abstract]
Number of options, exercisable, end of year (in shares) | shares	988,794
Weighted average exercise price, exercisable, end of year (in dollars per share) | $ / shares	$ 226.34
Weighted average remaining contractual life in years, outstanding, end of year	4 years 8 months 12 days
Weighted average remaining contractual life in years, exercisable, end of year	3 years 6 months
Aggregate intrinsic value, outstanding, end of year | $	$ 55,105
Aggregate intrinsic value, exercisable, end of year | $	$ 52,939