Interim Pension and Other Postretirement Benefit Plan Information (Details) - USD ($) $ in Thousands	3 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Defined Benefit Plan Disclosure [Line Items]
Contribution to postretirement medical plans	$ 4,000
Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Service cost	4,323	$ 4,612
Interest cost	5,063	5,028
Expected return on assets	(7,383)	(6,978)
Amortization of prior service cost (credit)	(58)	(58)
Amortization of actuarial (gain) loss	1,951	3,172
Net periodic pension cost	3,896	5,776
Other Benefits
Defined Benefit Plan Disclosure [Line Items]
Service cost	2,559	4,306
Interest cost	2,683	2,660
Expected return on assets	(3,312)	(2,614)
Amortization of prior service cost (credit)	(3,309)	43
Amortization of actuarial (gain) loss	0	0
Net periodic pension cost	(1,379)	$ 4,395
Minimum | Other Benefits
Defined Benefit Plan Disclosure [Line Items]
Expected future contributions	15,000
Maximum | Other Benefits
Defined Benefit Plan Disclosure [Line Items]
Expected future contributions	$ 25,000