Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2018
Cash Flows from Operating Activities:
Net income	$ 66,333	$ 169,044	$ 217,426
Adjustments to reconcile net income to net cash from operating activities:
Depreciation and amortization	968	1,017	1,248
Straight line office rent	154	391	201
Amortization expense related to other assets	9,416	9,416	9,416
Deferred income taxes	1,829	(3)	19,815
Operating expenses paid in The RMR Group Inc. common shares	3,785	4,948	4,348
Contingent consideration liability	0	0	(491)
Tax receivable agreement remeasurement	0	0	(24,710)
Distributions from equity method investments	736	549	174
Equity in (earnings) losses of investees	(1,545)	(719)	578
Impairment loss on Tremont Mortgage Trust investment	0	6,213	4,359
Unrealized (gain) loss on equity method investment accounted for under the fair value option	(3,151)	4,700	0
Changes in assets and liabilities:
Due from related parties	10,400	(64,849)	(3,736)
Prepaid and other current assets	1,971	(845)	318
Other client company reimbursable expenses	(9,830)	65,909	0
Accounts payable and accrued expenses	(3,569)	2,443	(476)
Net cash from operating activities	77,497	198,214	228,470
Cash Flows from Investing Activities:
Purchase of property and equipment	(601)	(702)	(648)
Equity method investment in TravelCenters of America Inc.	(5,319)	(8,382)	0
Equity method investment in Tremont Mortgage Trust	0	(5,650)	0
Advances to Tremont Mortgage Trust under the credit agreement	0	(14,220)	0
Repayments from Tremont Mortgage Trust under the credit agreement	0	14,220	0
Net cash used in investing activities	(5,920)	(14,734)	(648)
Cash Flows from Financing Activities:
Distributions to noncontrolling interest	(32,939)	(55,975)	(59,490)
Distributions to common shareholders	(24,789)	(22,727)	(16,169)
Repurchase of common shares	(523)	(827)	(987)
Payments under tax receivable agreement	(2,111)	(2,266)	(2,962)
Net cash used in financing activities	(60,362)	(81,795)	(79,608)
Effect of exchange rate fluctuations on cash and cash equivalents	0	(85)	(6)
Increase in cash and cash equivalents	11,215	101,600	148,208
Cash and cash equivalents at beginning of period	358,448	256,848	108,640
Cash and cash equivalents at end of period	369,663	358,448	256,848
Supplemental Cash Flow Information and Non-Cash Activities:
Income taxes paid	10,189	29,620	37,653
Fair value of share based payments recorded	4,912	6,461	7,421
Recognition of right of use assets and related lease liabilities	$ 40,765	$ 0	$ 0