Summary of Significant Accounting Policies - Components of Accumulated Other Comprehensive Loss (Details) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2017	Sep. 30, 2016
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning Balance	$ 60,370	$ 73,069
Other comprehensive income (loss) before reclassifications	2,699	(1,913)
Amounts reclassified from accumulated other comprehensive loss	900	1,051
Net current-period other comprehensive loss	3,599	(862)
Ending Balance	50,131	60,370
Foreign Currency Translation Adjustment
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning Balance	(5,623)	(5,731)
Other comprehensive income (loss) before reclassifications	1,016	108
Income tax benefit	0	0
Amounts reclassified from accumulated other comprehensive loss	0	0
Net current-period other comprehensive loss	1,016	108
Ending Balance	(4,607)	(5,623)
Retirement Plan Liability Adjustment
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning Balance	(7,197)	(6,257)
Other comprehensive income (loss) before reclassifications	1,655	(1,991)
Income tax benefit	3,758	3,758
Amounts reclassified from accumulated other comprehensive loss	894	1,051
Net current-period other comprehensive loss	2,549	(940)
Ending Balance	(4,648)	(7,197)
Interest Rates Swap Adjustment
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning Balance	(30)	0
Other comprehensive income (loss) before reclassifications	28	(30)
Income tax benefit	0	0
Amounts reclassified from accumulated other comprehensive loss	6	0
Net current-period other comprehensive loss	34	(30)
Ending Balance	4	(30)
Accumulated Other Comprehensive Loss
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning Balance	(12,850)	(11,988)
Ending Balance	$ (9,251)	$ (12,850)