Defined Benefit Pension and Other Postretirement Plans - Narrative (Details) - USD ($)	3 Months Ended		6 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Mar. 31, 2019	Mar. 31, 2018
Defined Benefit Plans and Other Postretirement Benefit Plans
Contribution made to pension and post-retirement plans			$ 5,000,000	$ 6,700,000
Expected contribution to pension plan during remainder of fiscal year	$ 6,500,000		6,500,000
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)	(100,000)	$ 200,000	(200,000)	300,000
Unfunded Plan | Nonqualified Plan
Defined Benefit Plans and Other Postretirement Benefit Plans
Defined benefit plan, net periodic benefit cost (credit)	$ 0	$ 0	$ 0	$ 0