Goodwill and Other Identifiable Intangible Assets - Changes in Carrying Amount of Goodwill by Segment (Detail) $ in Millions	6 Months Ended
	Jun. 30, 2026 USD ($)
Goodwill [Roll Forward]
Beginning Balance	$ 3,538.1
Foreign currency translation/other	(19.8)
Ending Balance	3,518.3
Previously Reported
Goodwill [Roll Forward]
Beginning Balance	3,538.1
Reallocation
Goodwill [Roll Forward]
Beginning Balance	0.0
Flow
Goodwill [Roll Forward]
Beginning Balance	641.2
Foreign currency translation/other	(11.4)
Ending Balance	629.8
Flow \| Previously Reported
Goodwill [Roll Forward]
Beginning Balance	967.5
Flow \| Reallocation
Goodwill [Roll Forward]
Beginning Balance	(326.3)
Flow \| Reallocation \| Fair Value Impact
Goodwill [Roll Forward]
Beginning Balance	(44.2)
Flow \| Reallocation \| Segment Composition
Goodwill [Roll Forward]
Beginning Balance	(282.1)
Water Solutions
Goodwill [Roll Forward]
Beginning Balance	1,733.4
Foreign currency translation/other	(8.4)
Ending Balance	1,725.0
Water Solutions \| Previously Reported
Goodwill [Roll Forward]
Beginning Balance	1,407.1
Water Solutions \| Reallocation
Goodwill [Roll Forward]
Beginning Balance	326.3
Water Solutions \| Reallocation \| Fair Value Impact
Goodwill [Roll Forward]
Beginning Balance	44.2
Water Solutions \| Reallocation \| Segment Composition
Goodwill [Roll Forward]
Beginning Balance	282.1
Pool
Goodwill [Roll Forward]
Beginning Balance	1,163.5
Foreign currency translation/other	0.0
Ending Balance	1,163.5
Pool \| Previously Reported
Goodwill [Roll Forward]
Beginning Balance	1,163.5
Pool \| Reallocation
Goodwill [Roll Forward]
Beginning Balance	$ 0.0