Quarterly Information (Unaudited) (Details) - USD ($) $ / shares in Units, $ 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
Quarterly Information (Unaudited)
Revenue	$ 136,939	$ 129,087	$ 129,535	$ 118,142	$ 108,246	$ 93,299	$ 95,304	$ 91,688	$ 513,703	$ 388,537	$ 334,179
Gross profit	66,143	62,431	57,900	57,335	52,536	39,263	41,663	38,686	243,809	172,148	134,604
Operating income (loss)	(21,241)	(883)	(9,321)	356	(1,382)	(12,051)	(11,145)	(12,022)	(31,089)	(36,600)	(47,431)
Income (loss) from continuing operations	(22,397)	(1,842)	(7,336)	2,706	(581)	(9,858)	(10,603)	(5,320)	(28,869)	(26,362)	(61,127)
Net income	$ 21,805	$ 39,166	$ 23,748	$ 26,028	$ 28,973	$ 13,696	$ 9,127	$ 13,057	$ 110,747	$ 64,853	$ 437,416
Basic net income per share (in dollars per share)	$ 0.29	$ 0.53	$ 0.32	$ 0.35	$ 0.39	$ 0.19	$ 0.12	$ 0.18	$ 1.49	$ 0.88	$ 6.08
Diluted net income per share (in dollars per share)	$ 0.29	$ 0.53	$ 0.32	$ 0.35	$ 0.39	$ 0.19	$ 0.12	$ 0.18	$ 1.49	$ 0.88	$ 6.04