Consolidated Statements of Shareholders’ Equity - USD ($) $ in Thousands	Total	Common shares Class A common stock	Common shares Class B-1 common stock	Common shares Class B-2 common stock	Additional Paid In Capital	Retained Earnings	Cumulative Other Comprehensive Income	Cumulative Common Distributions	Total Shareholders' Equity	Noncontrolling Interest
Balance beginning at Sep. 30, 2017	$ 289,663	$ 15	$ 1	$ 15	$ 95,878	$ 86,836	$ 84	$ (33,298)	$ 149,531	$ 140,132
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Share grants, net	3,361				3,361				3,361
Net income	217,426					96,041			96,041	121,385
Fees from services provided prior to our initial public offering	(127)									(127)
Tax distributions to Member	(44,490)									(44,490)
Common share distributions	(31,169)							(16,169)	(16,169)	(15,000)
Other comprehensive loss	(3)						(2)		(2)	(1)
Balance ending at Sep. 30, 2018	434,661	15	1	15	99,239	182,877	82	(49,467)	232,762	201,899
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Share grants, net	4,121				4,121				4,121
Net income	169,044					74,580			74,580	94,464
Tax distributions to Member	(37,975)									(37,975)
Common share distributions	(40,727)							(22,727)	(22,727)	(18,000)
Other comprehensive loss	(14)						(7)		(7)	(7)
Reclassification due to disposition of our Australian operations	(75)						(75)		(75)
Balance ending at Sep. 30, 2019	529,035	15	1	15	103,360	257,457	0	(72,194)	288,654	240,381
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Share grants, net	3,262				3,262				3,262
Net income	66,333					28,792			28,792	37,541
Tax distributions to Member	(14,939)									(14,939)
Common share distributions	(42,789)							(24,789)	(24,789)	(18,000)
Balance ending at Sep. 30, 2020	$ 540,902	$ 15	$ 1	$ 15	$ 106,622	$ 286,249	$ 0	$ (96,983)	$ 295,919	$ 244,983