Shareholders' Equity (Details) - USD ($)								1 Months Ended		3 Months Ended								5 Months Ended	12 Months Ended
	Dec. 14, 2015	Nov. 23, 2015	Sep. 24, 2015	Aug. 24, 2015	Jun. 05, 2015	May. 25, 2015	Feb. 26, 2015	Sep. 30, 2015	Mar. 31, 2013	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Jun. 05, 2015	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Jan. 23, 2015
Share Awards, additional disclosures
Closing share price of the entity's common shares (in dollars per share)			$ 16.12
Distributions
Cash distribution to common shareholders (in dollars per share)		$ 0.43		$ 0.43		$ 0.43	$ 0.43
Distribution payable to common shareholders (in dollars per share)																						$ 0.43
Common distributions declared (in dollars per share)										$ 0.56	$ 0.43	$ 0.43	$ 0.43	$ 0.43	$ 0.43	$ 0.43	$ 0.43		$ 1.72	$ 1.72	$ 1.72
Shares issued for each shares in connection with acquisition	0.0108
Payment in kind for each share	$ 0.1284
Characterization of distributions paid or accrued as a percentage of ordinary income																			47.44%	55.12%	82.92%
Characterization of distributions paid or accrued as a percentage of return of capital																			37.12%	41.94%	9.55%
Characterization of distributions paid or accrued as a percentage of capital gain																			12.90%		7.01%
Characterization of distributions paid or accrued as a percentage of Internal Revenue Code section 1250 gain																			1.61%	2.94%	0.52%
Characterization of distributions paid or accrued as a percentage of qualified dividend																			0.93%
Distribution paid to common shareholders																			$ (121,660,000)	$ (100,856,000)	$ (94,043,000)
Share Issuances
Number of shares issued																			23,222
Number of shares issued as partial payment to acquire Class A common stock of RMR Inc					700,000
Shares purchased from certain of our officers and other employees of RMR LLC			10,721
Closing share price of the entity's common shares (in dollars per share)			$ 16.12
Cumulative Other Comprehensive Income (Loss)
Balance at the beginning of the period													$ 37,000				$ 49,000	$ 37,000	$ 37,000	49,000	99,000
Other comprehensive loss before reclassifications																			(14,983,000)	37,000	(40,000)
Amounts reclassified from cumulative other comprehensive loss to net income																			79,000	(49,000)	(10,000)
Net current period other comprehensive loss																			(14,904,000)	(12,000)	(50,000)
Balance at the end of the period										$ (14,867,000)				$ 37,000					(14,867,000)	37,000	49,000
Unrealized Loss on Investment in Available for Sale Securities
Cumulative Other Comprehensive Income (Loss)
Other comprehensive loss before reclassifications																			(9,391,000)
Net current period other comprehensive loss																			(9,391,000)
Balance at the end of the period										(9,391,000)									(9,391,000)
Equity in Unrealized Gain (Loss) of an Investee
Cumulative Other Comprehensive Income (Loss)
Balance at the beginning of the period													$ 37,000				$ 49,000	$ 37,000	37,000	49,000	99,000
Other comprehensive loss before reclassifications																			(5,592,000)	37,000	(40,000)
Amounts reclassified from cumulative other comprehensive loss to net income																			79,000	(49,000)	(10,000)
Net current period other comprehensive loss																			(5,513,000)	(12,000)	(50,000)
Balance at the end of the period										$ (5,476,000)				$ 37,000					$ (5,476,000)	$ 37,000	$ 49,000
RMR LLC
Share Awards
Number of shares granted to each trustee under the award plan																			53,100	51,150	48,350
Aggregate market value of shares granted under the Award Plan																			$ 841,000	$ 1,191,000	$ 1,142,000
Number of Shares
Shares granted (in shares)																			53,100	51,150	48,350
Share Issuances
Number of shares issued									20,230									19,339		42,442
Shares purchased from certain of our officers and other employees of RMR LLC								10,721
Share Award Plan
Share Awards
Number of shares granted to each trustee under the award plan																			65,600	63,650	58,350
Number of Shares
Unvested shares at the beginning of the period													90,338				85,451	90,338	90,338	85,451	76,104
Shares granted (in shares)																			65,600	63,650	58,350
Shared forfeited or repurchased (in shares)																			(1,020)		(450)
Shares Vested (in shares)																			(58,193)	(58,763)	(48,553)
Unvested shares at the end of the period										96,725				90,338					96,725	90,338	85,451
Weighted Average Grant Date Fair Value
Unvested shares at the beginning of the period (in dollars per share)													$ 23.40				$ 23.71	$ 23.40	$ 23.40	$ 23.71	$ 23.82
Granted (in dollars per share)																			16.59	23.70	24.12
Shared forfeited or repurchased (in dollars per share)																			23.41		23.68
Vested (in dollars per share)																			21.20	24.17	24.38
Unvested shares at the end of the period (in dollars per share)										$ 20.11				$ 23.40					$ 20.11	$ 23.40	$ 23.71
Vesting schedule of unvested shares
2016 (in shares)										36,475									36,475
2017 (in shares)										29,100									29,100
2018 (in shares)										20,530									20,530
2019 (in shares)										10,620									10,620
Share Awards, additional disclosures
Estimated future compensation expense for the unvested shares										$ 1,535,000									$ 1,535,000
Closing share price of the entity's common shares (in dollars per share)										$ 15.87									$ 15.87
Weighted average period of recognition of compensation expenses																			22 months
Compensation expense																			$ 932,000	$ 1,165,000	$ 1,269,000
Shares available for issuance under the Award Plan										1,605,703									1,605,703
Share Issuances
Closing share price of the entity's common shares (in dollars per share)										$ 15.87									$ 15.87
Share Award Plan | Trustees
Share Awards
Number of shares granted to each trustee under the award plan																			2,500	2,500	2,000
Aggregate market value of shares granted under the Award Plan																			$ 247,000	$ 318,000	$ 266,000
Market value of common shares awarded to each trustee (in dollars)																			$ 49,000	$ 64,000	$ 53,000
Number of Shares
Shares granted (in shares)																			2,500	2,500	2,000
Class A common shares | RMR LLC
Distributions
Shares issued in connection with acquisition	768,032