Summary of Significant Accounting Policies - Components of Accumulated Other Comprehensive Loss (Details) - USD ($) $ in Thousands	12 Months Ended
Sep. 30, 2019	Sep. 30, 2018
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	$ 44,189	$ 50,131
Other comprehensive loss before reclassifications	(5,355)	4
Amounts reclassified from accumulated other comprehensive income (loss)	675	618
Net current-period other comprehensive loss	(4,680)	622
Ending balance	36,054	44,189
Foreign Currency Translation Adjustment
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	(4,955)	(4,607)
Other comprehensive loss before reclassifications	(712)	(348)
Amounts reclassified from accumulated other comprehensive income (loss)	0	0
Net current-period other comprehensive loss	(712)	(348)
Ending balance	(5,667)	(4,955)
AOCI tax benefit	0	0
Retirement Plan Liability Adjustment
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	(3,674)	(4,648)
Other comprehensive loss before reclassifications	(4,643)	333
Amounts reclassified from accumulated other comprehensive income (loss)	675	641
Net current-period other comprehensive loss	(3,968)	974
Ending balance	(7,642)	(3,674)
AOCI tax benefit	3,758	3,758
Interest Rates Swap Adjustment
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	0	4
Other comprehensive loss before reclassifications	0	19
Amounts reclassified from accumulated other comprehensive income (loss)	0	(23)
Net current-period other comprehensive loss	0	(4)
Ending balance	0	0
Accumulated Other Comprehensive Loss
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	(8,629)	(9,251)
Ending balance	$ (13,309)	$ (8,629)

A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

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Amount of tax expense (benefit) allocated to accumulated other comprehensive income (loss) attributable to parent.

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Amount after tax, before reclassification adjustments, of other comprehensive income (loss), attributable to parent.

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Amount after tax of other comprehensive income (loss) attributable to parent entity.

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Total of all stockholders' equity (deficit) items, net of receivables from officers, directors, owners, and affiliates of the entity which are attributable to the parent. The amount of the economic entity's stockholders' equity attributable to the parent excludes the amount of stockholders' equity which is allocable to that ownership interest in subsidiary equity which is not attributable to the parent (noncontrolling interest, minority interest). This excludes temporary equity and is sometimes called permanent equity.

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