Other Deductions, Net (Schedule Of Other Deductions, Net) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Mar. 31, 2019	Mar. 31, 2018
Other deductions, net [Line Items]
Amortization of intangibles	$ 60	$ 51	$ 117	$ 107
Restructuring costs	10	9	20	24
Other	(13)	28	(30)	35
Total	57	88	107	166
Increase (decrease) in intangibles amortization from acquisitions	13		29
Higher (lower) acquisition and divestiture related costs	(33)		(35)
Change in gain (loss) from foreign currency exchange transactions			10
Change in pension expense (income)	$ (11)		$ (22)
Pentair's Valves & Controls [Member] | Order or Production Backlog [Member]
Other deductions, net [Line Items]
Backlog amortization		$ 4		$ 19