Selected Quarterly Data (unaudited) - Quarterly Financial Information (Detail) - USD ($) $ / shares in Units, $ in Millions		3 Months Ended																12 Months Ended
		Dec. 31, 2019		Sep. 30, 2019		Jun. 30, 2019		Mar. 31, 2019		Dec. 31, 2018		Sep. 30, 2018		Jun. 30, 2018		Mar. 31, 2018		Dec. 31, 2019		Dec. 31, 2018		Dec. 31, 2017
Quarterly Financial Information [Line Items]
Loss on early extinguishment of debt																		$ 0.0		$ 17.1		$ 101.4
Net sales		$ 755.2		$ 713.6		$ 799.5		$ 688.9		$ 740.5		$ 711.4		$ 780.6		$ 732.6
Net sales	[1]																	2,957.2		2,965.1		2,845.7
Gross profit		274.2		255.0		286.7		235.6		268.0		243.8		282.6		253.3		1,051.5		1,047.7		987.5
Operating income		122.3		108.8		133.8		67.6		113.0		108.4		122.6		92.7		432.5		436.7		378.3
Net income from continuing operations		102.9		91.3		115.1		52.4		94.2	[2]	91.2		77.9	[3]	58.4		361.7		321.7		114.1
(Loss) income from discontinued operations, net of tax		(5.1)		1.0		(0.8)		(1.1)		(1.3)		18.9		(36.4)		44.5		(6.0)		25.7		371.3
Gain from sale of discontinued operations, net of tax																		0.0		0.0		181.1
Net income		$ 97.8		$ 92.3		$ 114.3		$ 51.3		$ 92.9		$ 110.1		$ 41.5		$ 102.9		$ 355.7		$ 347.4		$ 666.5
Earnings per ordinary share
Continuing operations (USD per share)		$ 0.61		$ 0.54		$ 0.68		$ 0.31		$ 0.55		$ 0.52		$ 0.44		$ 0.33		$ 2.14		$ 1.83		$ 0.63
Discontinued operations (USD per share)		(0.03)		0.01		(0.01)		(0.01)		(0.01)		0.11		(0.21)		0.24		(0.04)		0.15		3.04
Earnings Per Share, Basic (USD per share)		0.58	[4]	0.55	[4]	0.67	[4]	0.30	[4]	0.54	[2]	0.63	[2]	0.23	[2]	0.57	[2]	2.10	[4]	1.98	[2]	3.67
Continuing operations (USD per share)		0.61		0.54		0.68		0.30		0.54		0.52		0.44		0.32		2.12		1.81		0.62
Discontinued operations (USD per share)		(0.03)		0.01		(0.01)		0		(0.01)		0.11		(0.21)		0.25		(0.03)		0.15		3.01
Diluted		$ 0.58	[4]	$ 0.55	[4]	$ 0.67	[4]	$ 0.30	[4]	$ 0.53	[2]	$ 0.63	[2]	$ 0.23	[2]	$ 0.57	[2]	$ 2.09	[4]	$ 1.96	[2]	$ 3.63
Trade name and other impairment																		$ 21.2		$ 12.0		$ 15.6
Segment Reconciling Items [Member]
Quarterly Financial Information [Line Items]
Loss on early extinguishment of debt																		0.0		17.1		101.4
Earnings per ordinary share
Trade name and other impairment																		21.2		12.0		15.6
Mark-to-market actuarial gains (losses) on pension and post-retirement benefit plans																		(3.4)		3.6		8.5
Retained earnings
Quarterly Financial Information [Line Items]
Net income																		$ 355.7		$ 347.4		$ 666.5

[1] ⁽¹⁾  One customer in the Aquatic Systems segment, Pool Corporation, represented approximately 15% of our consolidated net sales in 2019, 2018 and 2017.

[2] ⁽²⁾  Amounts may not total to annual earnings because each quarter and year are calculated separately based on basic and diluted weighted-average ordinary shares outstanding during that period.

[3] ⁽¹⁾  Includes decrease of $17.1 million related to loss on early extinguishment of debt.

[4] ⁽¹⁾  Amounts may not total to annual earnings because each quarter and year are calculated separately based on basic and diluted weighted-average ordinary shares outstanding during that period.