Pension Plan and Retirement Benefits - Defined Benefit Plans - Recognized in BS (Details) - USD ($) $ in Thousands	Sep. 30, 2022	Sep. 30, 2021
Accrued pension and postretirement benefits:
Current	$ (3,371)	$ (3,554)
Non-current	(74,150)	(97,796)
Accrued pension and postretirement benefits	(77,521)	(101,350)
Accumulated other comprehensive income (loss):
Net income (loss)	(8,311)	8,446
Prior service cost	1,365	1,599
Total accumulated other comprehensive income (loss)	(6,946)	10,045
Accumulated benefit obligation	227,915	308,284
Defined Benefit Pension Plan
Accrued pension and postretirement benefits:
Non-current	(12,954)	(17,763)
Accrued pension and postretirement benefits	(12,954)	(17,763)
Accumulated other comprehensive income (loss):
Net income (loss)	22,496	19,150
Prior service cost	1,365	1,599
Total accumulated other comprehensive income (loss)	23,861	20,749
Defined Benefit Pension Plan | Other assets
Accrued pension and postretirement benefits:
Noncurrent assets	7,702	8,372
Non-current	(20,655)	(26,135)
Defined Benefit Other Postretirement Benefit Plan
Accrued pension and postretirement benefits:
Current	(3,276)	(3,459)
Non-current	(60,761)	(79,505)
Accrued pension and postretirement benefits	(64,037)	(82,964)
Accumulated other comprehensive income (loss):
Net income (loss)	(30,807)	(10,704)
Total accumulated other comprehensive income (loss)	(30,807)	(10,704)
Non Qualified Pension Plans Defined Benefit [Member]
Accrued pension and postretirement benefits:
Current	(95)	(95)
Non-current	(435)	(528)
Accrued pension and postretirement benefits	$ (530)	$ (623)