Debt - Additional Information (Detail)			3 Months Ended		12 Months Ended
	Sep. 30, 2024 USD ($)	Sep. 30, 2023 USD ($)	Mar. 31, 2025 USD ($) testingPeriod	Mar. 31, 2024 USD ($)	Dec. 31, 2024 USD ($)	Jun. 30, 2022 USD ($)
Debt Instrument [Line Items]
Repayments of long-term debt			$ 0	$ 6,300,000
Leverage ratio covenant period			12 months
Line of Credit | Term Loans Due 2024
Debt Instrument [Line Items]
Optional line of credit limit increase			$ 300,000,000.0
Line of Credit | Revolving Credit Facility
Debt Instrument [Line Items]
Credit facility maximum borrowing capacity			900,000,000.0
Available capacity			694,300,000
Debt, gross			$ 205,700,000		$ 9,500,000
Line of Credit | Revolving Credit Facility | Pentair, Pentair Finance S.à r.l (“PFSA“)
Debt Instrument [Line Items]
Number of testing periods | testingPeriod			4
Line of Credit | Revolving Credit Facility | Minimum
Debt Instrument [Line Items]
Debt covenant, unrestricted cash			$ 5,000,000.0
Debt agreement financial covenant, leverage ratio			1.00
EBITDA ratio for debt			1.00
Line of Credit | Revolving Credit Facility | Minimum | Pentair, Pentair Finance S.à r.l (“PFSA“)
Debt Instrument [Line Items]
Debt agreement financial covenant, leverage ratio			4.25
Line of Credit | Revolving Credit Facility | Maximum
Debt Instrument [Line Items]
Debt covenant, unrestricted cash			$ 250,000,000.0
Debt agreement financial covenant, leverage ratio			3.75
EBITDA ratio for debt			3.00
Line of Credit | Revolving Credit Facility | Maximum | Pentair, Pentair Finance S.à r.l (“PFSA“)
Debt Instrument [Line Items]
Debt agreement financial covenant, leverage ratio			1.00
Term Loans
Debt Instrument [Line Items]
Repayments of principal in next twelve months			$ 19,300,000
Term Loans | 5-year Term Loan Facility
Debt Instrument [Line Items]
Debt, gross			825,000,000.0		825,000,000.0
Unsecured Debt | 5-year Term Loan Facility
Debt Instrument [Line Items]
Debt, principal amount						$ 1,000,000,000
Debt installment payment amount	$ 12,500,000	$ 6,300,000
Repayments of long-term debt					$ 162,500,000
Debt, gross			825,000,000
Other Credit Facilities
Debt Instrument [Line Items]
Credit facility maximum borrowing capacity			20,800,000
Borrowings outstanding			$ 0