Shareholders' Equity (Details) $ / shares in Units, $ in Thousands						6 Months Ended	9 Months Ended
	Jul. 12, 2016 USD ($) $ / shares shares	May 19, 2016 USD ($) $ / shares shares	Mar. 09, 2016 director $ / shares shares	Dec. 15, 2015 USD ($) $ / shares shares	Nov. 25, 2015 USD ($) $ / shares	Dec. 14, 2015 $ / shares	Jun. 30, 2016 item shares	Sep. 30, 2015 shares
Class A membership units
Conversion ratio							1
Class A common shares
Common stock shares authorized							31,600,000	31,000,000
Number of votes per each share held | item							1
Dividend declared (in dollars per share) | $ / shares	$ 0.25
Dividend paid (in dollars per share) | $ / shares		$ 0.2993			$ 0.5260
Common stock shares outstanding							15,007,500	15,000,000
Class A common shares | Equity Compensation Plan | Independent Directors
Shares granted			2,500
Share value | $ / shares			$ 23.27
Number of independent directors | director			3
Class B-1 common shares
Common stock shares authorized							1,000,000	1,000,000
Number of votes per each share held | item							10
Conversion ratio							1
Dividend declared (in dollars per share) | $ / shares	$ 0.25
Dividend paid (in dollars per share) | $ / shares		$ 0.2993			$ 0.5260
Common stock shares outstanding							1,000,000	1,000,000
Class B-2 common shares
Common stock shares authorized							15,000,000	15,000,000
Number of votes per each share held | item							10
Common stock shares outstanding							15,000,000	15,000,000
Class A and Class B-1 Common Share
Dividend, Cash | $	$ 4,002	$ 4,791		$ 8,416	$ 8,416
Dividend paid (in dollars per share) | $ / shares		$ 0.25				$ 0.25
Common stock shares outstanding	16,007,500	16,007,500		16,007,500
ABP Trust | Class A common shares
Dividend, Cash | $	$ 3,750	$ 4,489		$ 7,890
Common stock shares outstanding	15,000,000	15,000,000		15,000,000
RMR LLC
Dividend declared (in dollars per share) | $ / shares	$ 0.25
Dividend, Cash | $	$ 7,752	$ 9,280		$ 16,306
Dividend paid (in dollars per share) | $ / shares		$ 0.2993		$ 0.5260
RMR LLC | Class A common shares | Equity Compensation Plan | Independent Directors
Shares granted			7,500