Summary of Significant Accounting Policies - Components of Accumulated Other Comprehensive Loss (Details) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2018	Sep. 30, 2017
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning Balance	$ 50,131	$ 60,370
Other comprehensive income (loss) before reclassifications	4	2,699
Amounts reclassified from accumulated other comprehensive loss (income)	618	900
Net current-period other comprehensive loss	622	3,599
Ending Balance	44,189	50,131
Foreign Currency Translation Adjustment
Accumulated Other Comprehensive Income (Loss) [Line Items]
Income tax benefit	0	0
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning Balance	(4,607)	(5,623)
Other comprehensive income (loss) before reclassifications	(348)	1,016
Amounts reclassified from accumulated other comprehensive loss (income)	0	0
Net current-period other comprehensive loss	(348)	1,016
Ending Balance	(4,955)	(4,607)
Retirement Plan Liability Adjustment
Accumulated Other Comprehensive Income (Loss) [Line Items]
Income tax benefit	3,758	3,758
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning Balance	(4,648)	(7,197)
Other comprehensive income (loss) before reclassifications	333	1,655
Amounts reclassified from accumulated other comprehensive loss (income)	641	894
Net current-period other comprehensive loss	974	2,549
Ending Balance	(3,674)	(4,648)
Interest Rates Swap Adjustment
Accumulated Other Comprehensive Income (Loss) [Line Items]
Income tax benefit	0	0
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning Balance	4	(30)
Other comprehensive income (loss) before reclassifications	19	28
Amounts reclassified from accumulated other comprehensive loss (income)	(23)	6
Net current-period other comprehensive loss	(4)	34
Ending Balance	0	4
Accumulated Other Comprehensive Loss
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning Balance	(9,251)	(12,850)
Ending Balance	$ (8,629)	$ (9,251)