Defined Benefit Pension and Other Postretirement Plans - Narrative (Details) - USD ($)	3 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Defined Benefit Plans and Other Postretirement Benefit Plans
Contribution made to pension and post-retirement plans	$ 3,200,000	$ 0
Expected contribution to pension plan during remainder of fiscal year		9,500,000
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)	0	(100,000)
Unfunded Plan | Nonqualified Plan
Defined Benefit Plans and Other Postretirement Benefit Plans
Defined benefit plan, net periodic benefit cost (credit)	$ 0	$ 0