Interim Pension and Other Postretirement Benefit Plan Information - Schedule of Components of Net Periodic Pension Cost (Details) - USD ($) $ in Thousands	3 Months Ended
	Dec. 31, 2024	Dec. 31, 2023
Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 2,837	$ 2,389
Interest cost	6,663	7,497
Expected return on assets	(7,655)	(7,202)
Amortization of prior service cost (credit)	0	0
Amortization of actuarial (gain) loss	256	118
Settlement	0	776
Net periodic pension cost	2,101	3,578
Other Benefits
Defined Benefit Plan Disclosure [Line Items]
Service cost	2,033	1,507
Interest cost	3,365	3,509
Expected return on assets	(3,831)	(3,128)
Amortization of prior service cost (credit)	(3,260)	(3,260)
Amortization of actuarial (gain) loss	(2,429)	(2,718)
Settlement	0	0
Net periodic pension cost	$ (4,122)	$ (4,090)