Summary of Significant Accounting Policies - Reclassification Out of Accumulated Other Comprehensive Loss (Details) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2018	Sep. 30, 2017
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Total before taxes	$ (7,531)	$ (13,140)
Income tax expense	(361)	1,069
Net loss	(7,170)	(14,209)
Reclassification out of Accumulated Other Comprehensive Income [Member] | Prior service costs
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Total before taxes	0	15
Reclassification out of Accumulated Other Comprehensive Income [Member] | Net actuarial loss
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Total before taxes	974	927
Reclassification out of Accumulated Other Comprehensive Income [Member] | Settlements/curtailments
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Total before taxes	0	(48)
Reclassification out of Accumulated Other Comprehensive Income [Member] | Retirement Plan Liability Adjustment
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Total before taxes	974	894
Income tax expense	0	0
Net loss	$ 974	$ 894