Leases - Balance sheet presentation (Details) $ in Thousands	Mar. 31, 2022 USD ($) serviceCenter	Sep. 30, 2021 USD ($)	Sep. 30, 2020 USD ($)
Assets
Finance leases		$ 18,252	$ 8,480
Operating leases		222,446	227,146
Total right-of-use assets		240,698	235,626
Current
Finance leases		452	165
Operating leases		37,688	35,716
Noncurrent
Finance leases		18,287	8,466
Operating leases		194,745	201,071
Total		$ 251,172	$ 245,418
Finance Lease, Right-of-Use Asset, Statement of Financial Position [Extensible List]		Public Utilities, Property, Plant and Equipment, Net	Public Utilities, Property, Plant and Equipment, Net
Operating Lease, Right-of-Use Asset, Statement of Financial Position [Extensible List]		Deferred charges and other assets (See Note 9)	Deferred charges and other assets (See Note 9)
Finance Lease, Liability, Current, Statement of Financial Position [Extensible List]		Current maturities of long-term debt	Current maturities of long-term debt
Operating Lease, Liability, Current, Statement of Financial Position [Extensible List]		Other current liabilities	Other current liabilities
Finance Lease, Liability, Noncurrent, Statement of Financial Position [Extensible List]		Long-term debt	Long-term debt
Operating Lease, Liability, Noncurrent, Statement of Financial Position [Extensible List]		Deferred credits and other liabilities	Deferred credits and other liabilities
Subsequent Event
Lessee, Lease, Description [Line Items]
Number of buildings leased | serviceCenter	2
Lessee, Finance Lease, Future Payments	$ 46,500