Earnings Per Share (Detail) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Computation Of Earnings Per Share Line Items
Net income	$ 103.0	$ 110.8	$ 72.1	$ 72.7	$ 97.8	$ 92.3	$ 114.3	$ 51.3	$ 358.6	$ 355.7	$ 347.4
Net income from continuing operations									$ 357.1	$ 361.7	$ 321.7
Weighted average common shares outstanding
Basic (shares)									166.5	169.4	175.8
Dilutive impact of stock options and restricted stock awards (shares)									0.9	1.0	1.5
Diluted (shares)									167.4	170.4	177.3
Earnings (loss) per ordinary share
Continuing operations (USD per share)	$ 0.60	$ 0.67	$ 0.44	$ 0.43	$ 0.61	$ 0.54	$ 0.68	$ 0.31	$ 2.14	$ 2.14	$ 1.83
Discontinued operations (USD per share)	0.02	0	(0.01)	0	(0.03)	0.01	(0.01)	(0.01)	0.01	(0.04)	0.15
Basic earnings (loss) per common share (USD per share)	0.62	0.67	0.43	0.43	0.58	0.55	0.67	0.30	2.15	2.10	1.98
Continuing operations (USD per share)	0.60	0.66	0.44	0.43	0.61	0.54	0.68	0.30	2.13	2.12	1.81
Discontinued operations (USD per share)	0.01	0	(0.01)	0	(0.03)	0.01	(0.01)	0	0.01	(0.03)	0.15
Diluted earnings (loss) per common share (USD per share)	$ 0.61	$ 0.66	$ 0.43	$ 0.43	$ 0.58	$ 0.55	$ 0.67	$ 0.30	$ 2.14	$ 2.09	$ 1.96
Anti-dilutive stock options excluded from the calculation of diluted earnings per share									1.7	2.1	1.2