Related Person Transactions - REITs, for which RMR LLC provides Management Services (Details) $ in Thousands				1 Months Ended			3 Months Ended		6 Months Ended	9 Months Ended
	Oct. 27, 2015 USD ($) room property	Jul. 23, 2015 USD ($) state room property	Jun. 01, 2015 property	Aug. 31, 2015 USD ($) company	Jul. 31, 2015 item	Jun. 30, 2015 USD ($)	Sep. 30, 2015 USD ($) property	Sep. 30, 2014 USD ($)	Sep. 30, 2015 USD ($) property	Sep. 30, 2015 USD ($) property	Sep. 30, 2014 USD ($)	Oct. 31, 2015 USD ($)	Apr. 28, 2015 USD ($)
Related Party Transaction [Line Items]
Rental income							$ 73,747	$ 63,837		$ 207,561	$ 190,959
Real Estate Aggregate Purchase Price							477,883		$ 477,883	477,883
Purchase price excluding closing cost							477,883		$ 477,883	477,883
Earnings (losses) recognized related to equity investments							$ (24)	38		$ 71	66
Sonesta ES Suites
Related Party Transaction [Line Items]
Amount expected to be provided for renovation for acquisitions made		$ 45,000
Sonesta agreements
Related Party Transaction [Line Items]
Number of real estate properties leased or managed | property							31		31	31
Management agreement fees and expenses							$ 5,742	4,722		$ 16,143	13,052
Procurement and construction supervision fees							496	1,053		1,172	2,803
Real Estate Aggregate Purchase Price													$ 750
Purchase price excluding closing cost													$ 750
Amount expected to be provided for renovation for acquisitions made										45,000
Hotels | Sonesta ES Suites
Related Party Transaction [Line Items]
Real Estate Aggregate Purchase Price		$ 85,000
Number of properties acquired | property		9
Number of hotel suites | room		1,095
Number of states hotels to be acquired located | state		8
Purchase price excluding closing cost		$ 85,000
Hotels | Sonesta ES Suites | Subsequent event
Related Party Transaction [Line Items]
Real Estate Aggregate Purchase Price	$ 12,000
Number of hotel suites | room	262
Purchase price excluding closing cost	$ 12,000
Number of hotels to be acquired | property	2
Hotels | Sonesta agreements
Related Party Transaction [Line Items]
Number of properties acquired | item					9
Travel Centers of America LLC
Related Party Transaction [Line Items]
Rental income							65,548	55,749		181,174	166,427
Real Estate Aggregate Purchase Price							279,383		$ 279,383	279,383
Number of properties acquired | property									14
Purchase price excluding closing cost							279,383		$ 279,383	279,383
Travel Centers of America LLC | Subsequent event
Related Party Transaction [Line Items]
Real Estate Aggregate Purchase Price												$ 15,000
Purchase price excluding closing cost												$ 15,000
Travel Centers of America LLC | Travel centers
Related Party Transaction [Line Items]
Number of properties acquired | property			5
RMR LLC
Related Party Transaction [Line Items]
Rental income							9			26
Number of entities to whom RMR provides management services | company				5
Aggregate coverage of combined directors' and officers' liability insurance policy purchased by the related party				$ 10,000
Aggregate additional coverage of combined directors' and officers' liability insurance policy purchased by the related party				20,000
Non-indemnifiable coverage of combined directors' and officers' liability insurance policy purchased by the related party				5,000
Premium paid for combined directors' and officers' liability insurance policy				$ 463
AIC
Related Party Transaction [Line Items]
Equity method investments, carrying value							6,814		$ 6,814	6,814
Earnings (losses) recognized related to equity investments							(24)	38		71	66
Equity in unrealized (loss) gain of an investee							$ (72)	$ (33)		$ (91)	$ 8
Combined property insurance policy term						3 years
Coverage of property insurance						$ 500,000
Terrorism property insurance term						1 year
Terrorism coverage of property insurance						$ 200,000
Property insurance premium						$ 2,442