Income Taxes - Narrative (Details) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2017	Sep. 30, 2016
Operating Loss Carryforwards [Line Items]
Alternative minimum tax	$ 28
Portion of tax loss carryforward offset by unrealized stock compensation deduction	5
Liability for uncertain tax positions, excluding any related interest and penalties	69	$ 69
Portion of liability related to uncertain tax position which, if recognized, would impact the effective tax rate	69
Accrued (reversal of accrued) interest	24
Interest and penalties from continuing operations	3
Undistributed earnings of foreign subsidiaries	11,427
Revenue commissioners, Ireland | Subsidiaries
Operating Loss Carryforwards [Line Items]
Operating loss carryforward	5,473
Foreign tax authority
Operating Loss Carryforwards [Line Items]
Tax credit carryforward	602
Domestic tax authority
Operating Loss Carryforwards [Line Items]
Tax credit carryforward	13,561
State tax authority
Operating Loss Carryforwards [Line Items]
Tax credit carryforward	165
State and local jurisdiction
Operating Loss Carryforwards [Line Items]
Operating loss carryforward	23,848
General Business Tax Credit Carryforward | Domestic tax authority
Operating Loss Carryforwards [Line Items]
Tax credit carryforward	$ 758