Defined Benefit Pension and Other Postretirement Plans - Narrative (Details) - USD ($)	3 Months Ended		9 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Defined Benefit Plans and Other Postretirement Benefit Plans
Contribution made to pension and post-retirement plans			$ 8,200,000	$ 10,100,000
Expected contribution to pension plan during remainder of fiscal year	$ 3,000,000.0		3,000,000.0
Other Postretirement Benefits
Defined Benefit Plans and Other Postretirement Benefit Plans
Contribution made to pension and post-retirement plans			0	0
Defined benefit plan, net periodic benefit cost (credit)	(100,000)	$ 300,000	(400,000)	500,000
Unfunded Plan | Nonqualified Plan
Defined Benefit Plans and Other Postretirement Benefit Plans
Defined benefit plan, net periodic benefit cost (credit)	$ 0	$ 0	$ 0	$ 0