Other Deductions, Net (Schedule Of Other Deductions, Net) (Details) - USD ($) $ in Millions	3 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Other deductions, net [Line Items]
Amortization of intangibles	$ 57	$ 56
Restructuring costs	10	15
Other	(17)	7
Total	50	78
Increase (decrease) in intangibles amortization from acquisitions	17
Change in gain (loss) from foreign currency exchange transactions	13
Change in pension expense (income)	$ (11)
Pentair's Valves & Controls [Member] | Order or Production Backlog [Member]
Other deductions, net [Line Items]
Backlog amortization		$ 15