Selected Quarterly Data (unaudited) - Quarterly Financial Information (Detail) - USD ($) $ / shares in Units, $ in Millions		3 Months Ended																12 Months Ended
		Dec. 31, 2018		Sep. 30, 2018		Jun. 30, 2018		Mar. 31, 2018		Dec. 31, 2017		Sep. 30, 2017		Jun. 30, 2017		Mar. 31, 2017		Dec. 31, 2018		Dec. 31, 2017		Dec. 31, 2016
Quarterly Financial Information [Line Items]
Loss on early extinguishment of debt																		$ 17.1		$ 101.4		$ 0.0
Net sales		$ 740.5		$ 711.4		$ 780.6		$ 732.6		$ 720.8		$ 687.6		$ 754.0		$ 683.3
Net sales	[1]																	2,965.1		2,845.7		2,780.6
Gross profit		268.0		243.8		282.6		253.3		253.7		236.5		273.6		223.7		1,047.7		987.5		959.1
Operating income		113.0		108.4		122.6		92.7		85.4		101.8		129.2		61.9		436.7		378.3		354.4
Net income from continuing operations		94.2		91.2		77.9	[2]	58.4		55.8	[3]	49.0		(3.4)	[4]	12.7		321.7		114.1		178.2
Income (loss) from discontinued operations, net of tax		(1.3)		18.9		(36.4)		44.5		151.6		78.2		66.5		75.0		25.7		371.3		343.4
Gain from sale / impairment of discontinued operations, net of tax										(17.8)		(1.7)		200.6		0.0		0.0		181.1		0.6
Net income		$ 92.9		$ 110.1		$ 41.5		$ 102.9		$ 189.6		$ 125.5		$ 263.7		$ 87.7		$ 347.4		$ 666.5		$ 522.2
Earnings per ordinary share
Continuing operations (USD per share)		$ 0.55		$ 0.52		$ 0.44		$ 0.33		$ 0.32		$ 0.27		$ (0.02)		$ 0.07		$ 1.83		$ 0.63		$ 0.98
Discontinued operations (USD per share)		(0.01)		0.11		(0.21)		0.24		0.73		0.42		1.47		0.41		0.15		3.04		1.90
Earnings Per Share, Basic (USD per share)		0.54	[5]	0.63	[5]	0.23	[5]	0.57	[5]	1.05	[6]	0.69	[6]	1.45	[6]	0.48	[6]	1.98	[5]	3.67	[6]	2.88
Continuing operations (USD per share)		0.54		0.52		0.44		0.32		0.30		0.27		(0.02)		0.07		1.81		0.62		0.97
Discontinued operations (USD per share)		(0.01)		0.11		(0.21)		0.25		0.74		0.41		1.45		0.41		0.15		3.01		1.88
Diluted		$ 0.53	[5]	$ 0.63	[5]	$ 0.23	[5]	$ 0.57	[5]	$ 1.04	[6]	$ 0.68	[6]	$ 1.43	[6]	$ 0.48	[6]	$ 1.96	[5]	$ 3.63	[6]	$ 2.85
Impairment of trade names																		$ 12.0		$ 15.6		$ 0.0
Segment Reconciling Items [Member]
Quarterly Financial Information [Line Items]
Loss on early extinguishment of debt																		17.1		101.4		0.0
Earnings per ordinary share
Impairment of trade names																		12.0		15.6		0.0
Mark-to-market actuarial gains (losses) on pension and post-retirement benefit plans																		3.6		8.5		(12.0)
Retained earnings
Quarterly Financial Information [Line Items]
Net income																		$ 347.4		$ 666.5		$ 522.2

[1] (1) One customer in the Aquatic Systems segment, Pool Corporation, represented approximately 15% of our consolidated net sales in 2018, 2017 and 2016.

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

[3] (2) Includes decrease of $15.6 million due to trade name and other impairment and $8.5 million related to a “mark-to-market” actuarial loss on pension and other post-retirement benefit plans.

[4] (1) Includes decrease of $101.4 million related to loss on early extinguishment of debt.

[5] (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.

[6] (3) 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.