Acquisitions (Details) $ in Thousands		12 Months Ended
	Nov. 19, 2018 USD ($) employee	Sep. 30, 2019 USD ($) employee	Sep. 30, 2018 USD ($)	Sep. 30, 2017 USD ($)
Acquisition-related cost		$ 3,100	$ 500	$ 1,600
Frustum [Member]
Total purchase price allocation, net of cash acquired	$ 69,500
Acquisition of businesses, net cash acquired	$ 700
Entity Number of Employees | employee	12
Goodwill acquired	$ 53,700	53,673
Finite-lived Intangible Assets Acquired	17,900
Total allocation of purchase price consideration	$ 2,100
Weighted average useful lives of acquired intangible assets	15 years
Other acquisitions [Member]
Total purchase price allocation, net of cash acquired		17,300
Acquisition of businesses, net cash acquired		$ 300
Entity Number of Employees | employee		95
Goodwill acquired		$ 12,645	$ 4,350
Finite-lived Intangible Assets Acquired		3,400
Total allocation of purchase price consideration		$ 1,300