Net Income Attributable to RMR Inc. (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Mar. 31, 2022	Mar. 31, 2021	Mar. 31, 2022	Mar. 31, 2021
Net Income Attributable to RMR Inc.
Income before income tax expense	$ 17,040	$ 13,472	$ 38,386	$ 35,981
RMR Inc. franchise tax expense and interest income	169	217	336	429
Net income before noncontrolling interest	17,209	13,689	38,722	36,410
Net income attributable to noncontrolling interest	(8,197)	(6,539)	(18,447)	(17,395)
Net income attributable to RMR Inc. before income tax expense	9,012	7,150	20,275	19,015
Income tax expense attributable to RMR Inc.	(2,451)	(1,992)	(5,505)	(4,748)
RMR Inc. franchise tax expense and interest income	(169)	(217)	(336)	(429)
Net income attributable to The RMR Group Inc.	$ 6,392	$ 4,941	$ 14,434	$ 13,838