Geographic Information - Schedule of Revenues from External Customers by Geographical Areas (Details) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2016
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenues	$ 448,716	$ 395,911	$ 565,243
United States
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenues	335,743	279,352	405,298
Canada
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenues	42,235	45,540	77,252
Middle East and Africa
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenues	38,490	26,639	40,294
Far East
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenues	12,976	3,877	7,895
Europe
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenues	10,538	21,194	26,200
Mexico, Central and South America
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenues	$ 8,734	$ 19,309	$ 8,304