Interim Pension and Other Postretirement Benefit Plan Information (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Mar. 31, 2023	Mar. 31, 2022	Mar. 31, 2023	Mar. 31, 2022
Defined Benefit Plan Disclosure [Line Items]
Contribution to postretirement medical plans			$ 6,200
Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 2,908	$ 4,324	5,816	$ 8,647
Interest cost	7,325	5,064	14,650	10,127
Expected return on assets	(7,278)	(7,383)	(14,556)	(14,766)
Amortization of prior service cost (credit)	(30)	(58)	(61)	(116)
Amortization of actuarial (gain) loss	164	1,951	329	3,902
Net periodic pension cost	3,089	3,898	6,178	7,794
Other Benefits
Defined Benefit Plan Disclosure [Line Items]
Service cost	1,546	2,558	3,091	5,117
Interest cost	3,478	2,684	6,955	5,367
Expected return on assets	(2,804)	(3,313)	(5,608)	(6,625)
Amortization of prior service cost (credit)	(3,285)	(3,308)	(6,571)	(6,617)
Amortization of actuarial (gain) loss	(1,863)	0	(3,726)	0
Net periodic pension cost	(2,928)	$ (1,379)	(5,859)	$ (2,758)
Other Benefits | Minimum
Defined Benefit Plan Disclosure [Line Items]
Expected future contributions	15,000		15,000
Other Benefits | Maximum
Defined Benefit Plan Disclosure [Line Items]
Expected future contributions	$ 25,000		$ 25,000