Income Taxes - Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Sep. 30, 2019
Deferred tax assets:
Loss and credit carryforwards	$ 31,015	$ 26,702
Compensation benefits	29,640	23,931
Operating lease liabilities	21,827	0
Other assets	9,000	9,393
Deferred tax assets, gross	91,482	60,026
Less valuation allowance	(24,563)	(19,231)
Total deferred tax assets	66,919	40,795
Deferred tax liabilities:
Intangible assets	(14,715)	(15,114)
Deferred commission	(9,027)	(7,920)
Property and equipment	(3,135)	(3,511)
Operating lease right-of-use assets	(13,719)	0
Other liabilities	(11,694)	(8,244)
Total deferred tax liabilities	(52,290)	(34,789)
Deferred tax assets, net	$ 14,629	$ 6,006