Summary of Significant Accounting Policies - Reclassification Out of Accumulated Other Comprehensive Loss (Details) - USD ($) $ in Thousands		12 Months Ended
		Sep. 30, 2016	Sep. 30, 2015
Net actuarial loss
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Amount reclassified from accumulated other comprehensive loss, before taxes	[1]	$ (828)	$ (545)
Settlements/curtailments
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Amount reclassified from accumulated other comprehensive loss, before taxes	[1]	223	0
Retirement Plan Liability Adjustment
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Amount reclassified from accumulated other comprehensive loss, before taxes		1,051	545
Income tax expense		0	(199)
Net of taxes		$ 1,051	$ 346

[1] These accumulated other comprehensive income components are included in the computation of net periodic benefit cost. See Note 7 - Retirement benefit plans for further information.