Segment and Geographic Information - Net Revenues based upon Source of Order by Geographic Area (Details) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2015
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenue	$ 692,885	$ 560,323	$ 552,708
North America
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenue	242,331	209,727	199,103
UNITED STATES
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenue	240,600	208,300	197,400
Asia/Pacific
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenue	327,864	247,241	231,840
United Kingdom
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenue	42,138	36,611	32,160
Rest of Europe
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenue	$ 80,552	$ 66,744	$ 89,605