Quarterly Information (Unaudited) - Schedule of Quarterly Information (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
Total revenues	$ 192,444	$ 174,033	$ 184,939	$ 178,135	$ 166,839	$ 210,224	$ 223,280	$ 222,435	$ 729,551	$ 822,777	$ 847,229
Net revenues	119,326	108,021	113,748	108,390	89,596	102,175	127,362	130,069	449,485	449,201	494,448
Net income (loss)	$ 1,553	$ (2,570)	$ 5,330	$ 4,299	$ (23,340)	$ (5,487)	$ (40,874)	$ 1,238	$ 8,612	$ (68,463)	$ 2,541
Basic earnings (loss) per share (in dollars per share)	$ 0.03	$ (0.05)	$ 0.10	$ 0.08	$ (0.42)	$ (0.10)	$ (0.74)	$ 0.02	$ 0.15	$ (1.24)	$ 0.05
Diluted earnings (loss) per share (in dollars per share)	$ 0.03	$ (0.05)	$ 0.10	$ 0.08	$ (0.42)	$ (0.10)	$ (0.74)	$ 0.02	$ 0.15	$ (1.24)	$ 0.05