Share Plans - Stock Option Activity (Detail) $ / shares in Units, shares in Millions, $ in Millions	12 Months Ended
	Dec. 31, 2023 USD ($) $ / shares shares
Shares
Beginning balance (shares) | shares	2.3
Granted (shares) | shares	0.3
Exercised (shares) | shares	(0.3)
Ending balance (shares) | shares	2.3
Options exercisable | shares	1.7
Options expected to vest at end of period | shares	0.6
Weighted Average Exercise Price
Beginning balance (USD per share) | $ / shares	$ 45.16
Granted (USD per share) | $ / shares	47.34
Exercised (USD per share) | $ / shares	47.35
Ending Balance (USD per share) | $ / shares	45.07
Options exercisable at end of period (USD per share) | $ / shares	42.39
Options expected to vest at end of period (USD per share) | $ / shares	$ 53.15
Weighted Average Remaining Contractual Life
Ending balance	4 years 10 months 24 days
Options exercisable at end of period	3 years 8 months 12 days
Options expected to vest at end of period	8 years 3 months 18 days
Aggregate Intrinsic value
Balance at end of period | $	$ 63.7
Options exercisable at end of period | $	52.4
Options expected to vest at end of period | $	$ 10.9