Segment Reporting (Details) $ in Thousands	3 Months Ended		9 Months Ended
	Jun. 30, 2017 USD ($)	Jun. 30, 2016 USD ($)	Jun. 30, 2017 USD ($) segment	Jun. 30, 2016 USD ($)
Segment Reporting
Number of reportable business segments | segment			1
Revenues:
Management services	$ 44,644	$ 41,867	$ 183,036	$ 182,940
Reimbursable payroll and related costs	9,839	9,744	29,023	25,993
Advisory services	1,019	600	3,033	1,741
Total revenues	55,502	52,211	215,092	210,674
Expenses:
Compensation and benefits	24,769	22,719	72,550	65,584
Separation costs	0	1,195	0	1,358
General and administrative	8,539	6,110	21,526	19,110
Depreciation and amortization	467	349	1,550	1,333
Total expenses	33,775	30,373	95,626	87,385
Operating income (loss)	21,727	21,838	119,466	123,289
Interest and other income	402	68	1,059	144
Income before income tax expense and equity in earnings of investee	22,129	21,906	120,525	123,433
Income tax expense	(4,528)	(4,504)	(24,811)	(19,904)
Equity in earnings of investee	4	0	(161)	0
Net income (loss)	17,605	17,402	95,553	103,529
Intersegment Eliminations
Revenues:
Total revenues	221	192	872	737
RMR LLC
Revenues:
Management services	44,644	41,867	183,036	182,882
Reimbursable payroll and related costs	9,839	9,744	29,023	25,993
Advisory services	0	0	0	0
Total revenues	54,483	51,611	212,059	208,875
Expenses:
Compensation and benefits	24,088	22,445	70,842	64,712
Separation costs		1,195		1,358
General and administrative	8,057	5,778	20,539	18,234
Depreciation and amortization	321	349	1,072	1,333
Total expenses	32,466	29,767	92,453	85,637
Operating income (loss)	22,017	21,844	119,606	123,238
Interest and other income	377	62	657	137
Income before income tax expense and equity in earnings of investee	22,394	21,906	120,263	123,375
Income tax expense	0	0	0	(1)
Equity in earnings of investee	0		0
Net income (loss)	22,394	21,906	120,263	123,374
All Other Operations
Revenues:
Management services	0	0	0	58
Reimbursable payroll and related costs	0	0	0	0
Advisory services	1,019	600	3,033	1,741
Total revenues	1,019	600	3,033	1,799
Expenses:
Compensation and benefits	681	274	1,708	872
Separation costs		0		0
General and administrative	482	332	987	876
Depreciation and amortization	146	0	478	0
Total expenses	1,309	606	3,173	1,748
Operating income (loss)	(290)	(6)	(140)	51
Interest and other income	25	6	402	7
Income before income tax expense and equity in earnings of investee	(265)	0	262	58
Income tax expense	(4,528)	(4,504)	(24,811)	(19,903)
Equity in earnings of investee	4		(161)
Net income (loss)	$ (4,789)	$ (4,504)	$ (24,710)	$ (19,845)