Geographic Information - Schedule of Revenues from External Customers by Geographical Areas (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 revenues	$ 395,911	$ 565,243	$ 661,858
United States
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenues	279,352	405,298	474,038
Canada
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenues	45,540	77,252	101,191
Middle East and Africa
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenues	26,639	40,294	40,557
Europe
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenues	21,194	26,200	23,567
Mexico, Central and South America
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenues	19,309	8,304	10,479
Far East
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenues	$ 3,877	$ 7,895	$ 12,026