Other Comprehensive Loss (Gains (losses) in Accumulated Other Comprehensive Loss) (Details) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2019
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Accumulated other comprehensive income (loss), beginning balance	$ 480,144
Accumulated other comprehensive income (loss), ending balance	580,671	$ 480,144
Accumulated Foreign Currency Adjustment Attributable to Parent [Member]
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Accumulated other comprehensive income (loss), beginning balance	(5,535)	(2,705)	$ (4,212)
Other comprehensive income (loss) before reclassifications	21,672	(2,830)	1,507
Amounts gains reclassified from accumulated other comprehensive loss into earnings	0	0	0
Accumulated other comprehensive income (loss), ending balance	16,137	(5,535)	(2,705)
Accumulated Defined Benefit Plans Adjustment Attributable to Parent [Member]
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Accumulated other comprehensive income (loss), beginning balance	(10,396)	(10,475)	(4,907)
Other comprehensive income (loss) before reclassifications	1,880	(927)	(5,939)
Amounts gains reclassified from accumulated other comprehensive loss into earnings	1,042	1,006	371
Accumulated other comprehensive income (loss), ending balance	(7,474)	(10,396)	(10,475)
Accumulated Gain (Loss), Net, Cash Flow Hedge, Parent [Member]
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Accumulated other comprehensive income (loss), beginning balance	(4,541)	176	102
Other comprehensive income (loss) before reclassifications	4,909	(5,375)	(424)
Amounts gains reclassified from accumulated other comprehensive loss into earnings	2,384	658	498
Accumulated other comprehensive income (loss), ending balance	$ 2,752	$ (4,541)	$ 176