Other Deductions, Net (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2017
Other deductions, net [Line Items]
Amortization of intangibles (intellectual property and customer relationships)	$ 238	$ 211	$ 136
Restructuring costs	95	65	78
Other	(8)	61	110
Other deductions, net	325	337	324
Increase (decrease) in intangibles amortization from acquisitions	46
Acquisition and divestiture related costs	(29)	18
Change in pension expense (income)	(42)	$ (78)
Change in gain (loss) from foreign currency transactions	13
Pentair's Valves & Controls [Member]
Other deductions, net [Line Items]
Restructuring costs			$ 25
Order or Production Backlog [Member] | Pentair's Valves & Controls [Member]
Other deductions, net [Line Items]
Amortization of intangibles (intellectual property and customer relationships)	$ 19