Segment and Geographic Information - Net Revenues Based upon Source of Order by Geographic Area (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Sep. 30, 2021	Jun. 30, 2021	Mar. 31, 2021	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2019
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenue	$ 136,939	$ 129,087	$ 129,535	$ 118,142	$ 108,246	$ 93,299	$ 95,304	$ 91,688	$ 513,703	$ 388,537	$ 334,179
North America
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenue									323,982	256,174	226,395
UNITED STATES
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenue									320,800	253,500	224,500
Asia/Pacific/Other
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenue									80,916	58,208	47,803
Europe
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenue									$ 108,805	$ 74,155	$ 59,981