Segment and Geographic Information - Long-Lived Assets, Consisting of Property, Plant and Equipment by Geographic Area (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Sep. 30, 2017
Revenues from External Customers and Long-Lived Assets [Line Items]
Property, plant and equipment, net	$ 59,988	$ 56,981
North America
Revenues from External Customers and Long-Lived Assets [Line Items]
Property, plant and equipment, net	50,614	50,908
UNITED STATES
Revenues from External Customers and Long-Lived Assets [Line Items]
Property, plant and equipment, net	50,500	50,700
Asia/Pacific
Revenues from External Customers and Long-Lived Assets [Line Items]
Property, plant and equipment, net	492	547
United Kingdom
Revenues from External Customers and Long-Lived Assets [Line Items]
Property, plant and equipment, net	5,494	2,848
Rest of Europe
Revenues from External Customers and Long-Lived Assets [Line Items]
Property, plant and equipment, net	$ 3,388	$ 2,678