Comprehensive Income (Loss) and Changes in Accumulated Other Comprehensive Income (Loss) by Component - Other (Details) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2021
Accumulated other comprehensive income (loss)
Balance	$ 375,488	$ 343,321	$ 301,501
Other comprehensive income (loss)	17,465	1,249	62,260
Balance	434,324	375,488	343,321
Accumulated Other Comprehensive Income (Loss)
Accumulated other comprehensive income (loss)
Balance	(11,092)	(12,341)	(74,601)
Other comprehensive income (loss) before reclassifications	19,037	1,250
Amounts reclassified from accumulated other comprehensive income (loss), Tax provision (benefit)	474
Other comprehensive income (loss)	17,465	1,249	62,260
Balance	6,373	(11,092)	(12,341)
Accumulated Defined Benefit Plans Adjustment | Defined Benefit Pension Plan
Accumulated other comprehensive income (loss)
Balance	(17,165)	(14,791)
Other comprehensive income (loss) before reclassifications	1,401	(2,557)
Amounts reclassified from accumulated other comprehensive income (loss), Tax provision (benefit)	(55)	(56)
Other comprehensive income (loss)	1,579	(2,374)
Balance	(15,586)	(17,165)	(14,791)
Accumulated Defined Benefit Plans Adjustment | Defined Benefit Other Postretirement Benefit Plan
Accumulated other comprehensive income (loss)
Balance	24,457	9,017
Other comprehensive income (loss) before reclassifications	10,907	15,624
Amounts reclassified from accumulated other comprehensive income (loss), Tax provision (benefit)	529	56
Other comprehensive income (loss)	9,157	15,440
Balance	33,614	24,457	9,017
Pension and postretirement: Less: amortization of prior service cost
Accumulated other comprehensive income (loss)
Amounts reclassified from accumulated other comprehensive income (loss), before tax	233	239
Other comprehensive income (loss)	178	183	176
Pension and postretirement: Less: amortization of prior service cost | Defined Benefit Pension Plan
Accumulated other comprehensive income (loss)
Amounts reclassified from accumulated other comprehensive income (loss), before tax	233	239
Pension and postretirement: Less: amortization of gain (loss)
Accumulated other comprehensive income (loss)
Amounts reclassified from accumulated other comprehensive income (loss), before tax	(2,279)	(240)
Other comprehensive income (loss)	(1,750)	(184)	5,933
Pension and postretirement: Less: amortization of gain (loss) | Defined Benefit Other Postretirement Benefit Plan
Accumulated other comprehensive income (loss)
Amounts reclassified from accumulated other comprehensive income (loss), before tax	(2,279)	(240)
Accumulated Translation Adjustment
Accumulated other comprehensive income (loss)
Balance	(18,384)	(6,567)
Other comprehensive income (loss) before reclassifications	6,729	(11,817)
Other comprehensive income (loss)	6,729	(11,817)	3,254
Balance	$ (11,655)	$ (18,384)	$ (6,567)