Stock-based compensation - Stock Options Outstanding and Activity During the Period (Detail) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023
Options Outstanding
Beginning balance (in shares)	1,100,000
Granted (in shares)	100,000
Exercised (in shares)	(300,000)
Canceled/Forfeited (in shares)	(0.0)
Expired (in shares)	0.0
Ending balance (in shares)	900,000	1,100,000
Vested and expected to vest after end of year (in shares)	900,000
Exercisable as of end of year (in shares)	700,000
Weighted- Average Exercise Price
Beginning Balance (in dollars per share)	$ 41.38
Granted (in dollars per share)	85.18
Exercised (in dollars per share)	35.71
Canceled/Forfeited (in dollars per share)	61.44
Expired (in dollars per share)	28.64
Ending Balance (in dollars per share)	47.54	$ 41.38
Vested and expected to vest after end of year (in dollars per share)	47.22
Exercisable as of end of year (in dollars per share)	$ 39.34
Weighted- Average Remaining Contractual Term (Years)
Balance	5 years 7 months 6 days	5 years 9 months 18 days
Vested and expected to vest after end of year	5 years 7 months 6 days
Exercisable as of end of year	4 years 8 months 12 days
Aggregate Intrinsic Value
Balance	$ 51.2	$ 51.3
Vested and expected to vest after end of year	51.0
Exercisable as of end of year	$ 44.5