Geographic Information - Schedule of Revenues from External Customers by Geographical Areas (Details) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2017
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues	$ 517,180	$ 448,716	$ 395,911
United States
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues	406,609	335,743	279,352
Canada
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues	64,326	42,235	45,540
Middle East and Africa
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues	18,420	38,490	26,639
Far East
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues	11,405	12,976	3,877
Europe
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues	13,746	10,538	21,194
Mexico, Central and South America
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues	$ 2,674	$ 8,734	$ 19,309