v3.26.1
Interim Pension and Other Postretirement Benefit Plan Information (Details) - USD ($)
$ in Thousands
 3 Months Ended 9 Months Ended
Jun. 30, 2026
Jun. 30, 2025
Jun. 30, 2026
Jun. 30, 2025
Pension Benefits        
Defined Benefit Plan Disclosure [Line Items]        
Service cost $ 2,580 $ 2,838 $ 7,740 $ 8,512
Interest cost 6,924 6,663 20,774 19,989
Expected return on assets (7,949) (7,655) (23,847) (22,964)
Amortization of prior service cost (credit) 0 0 0 0
Amortization of actuarial (gain) loss (51) 256 (153) 767
Net periodic pension cost 1,504 2,102 4,514 6,304
Other Benefits        
Defined Benefit Plan Disclosure [Line Items]        
Service cost 2,018 2,033 6,052 6,099
Interest cost 3,634 3,365 10,904 10,096
Expected return on assets (4,069) (3,831) (12,209) (11,494)
Amortization of prior service cost (credit) (2,880) (3,260) (8,639) (9,780)
Amortization of actuarial (gain) loss (2,414) (2,429) (7,244) (7,287)
Net periodic pension cost $ (3,711) $ (4,122) $ (11,136) $ (12,366)