Segment Information - Financial Information By Reportable Segment (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2025	Sep. 30, 2024	Dec. 31, 2024
Segment Reporting Information [Line Items]
Identifiable assets	$ 6,759.6		$ 6,759.6		$ 6,446.5
Capital expenditures	17.4	$ 15.4	45.1	$ 51.7
Depreciation	15.3	14.9	44.7	45.3
Operating Segments
Segment Reporting Information [Line Items]
Identifiable assets	6,329.6		6,329.6		6,005.5
Capital expenditures	16.9	12.0	39.7	42.3
Depreciation	13.2	13.0	38.3	38.9
Corporate and other
Segment Reporting Information [Line Items]
Identifiable assets	430.0		430.0		441.0
Capital expenditures	0.5	3.4	5.4	9.4
Depreciation	2.1	1.9	6.4	6.4
Flow | Operating Segments
Segment Reporting Information [Line Items]
Identifiable assets	2,005.3		2,005.3		1,590.7
Capital expenditures	4.9	4.4	11.8	11.6
Depreciation	5.2	5.4	15.6	16.2
Water Solutions | Operating Segments
Segment Reporting Information [Line Items]
Identifiable assets	2,574.5		2,574.5		2,613.5
Capital expenditures	4.0	3.7	9.7	18.6
Depreciation	3.9	4.1	11.9	12.9
Pool | Operating Segments
Segment Reporting Information [Line Items]
Identifiable assets	1,749.8		1,749.8		$ 1,801.3
Capital expenditures	8.0	3.9	18.2	12.1
Depreciation	$ 4.1	$ 3.5	$ 10.8	$ 9.8