Segment Information - Schedule of Revenues from External Customers by Geographical Areas (Details) $ in Thousands	12 Months Ended
	Sep. 30, 2020 USD ($) numberOfSegments	Sep. 30, 2019 USD ($)	Sep. 30, 2018 USD ($)
Revenues from External Customers and Long-Lived Assets [Line Items]
Reportable segments | numberOfSegments	1
Revenues	$ 518,499	$ 517,180	$ 448,716
United States
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues	397,983	406,609	335,743
Canada
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues	66,064	64,326	42,235
Middle East and Africa
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues	18,162	18,420	38,490
Far East
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues	18,079	11,405	12,976
Europe
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues	15,866	13,746	10,538
Mexico, Central and South America
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues	$ 2,345	$ 2,674	$ 8,734