Related Person Transactions (Details) (USD $)	0 Months Ended	3 Months Ended		6 Months Ended			3 Months Ended		6 Months Ended			0 Months Ended			0 Months Ended					1 Months Ended	3 Months Ended		6 Months Ended			0 Months Ended		0 Months Ended	3 Months Ended		5 Months Ended	6 Months Ended	0 Months Ended	6 Months Ended		0 Months Ended	3 Months Ended		6 Months Ended				6 Months Ended	0 Months Ended				0 Months Ended
	Jun. 02, 2014 item	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013	Dec. 31, 2013	Jun. 30, 2014 SIR	Jun. 30, 2013 SIR	Jun. 30, 2014 SIR	Jun. 30, 2013 SIR	Mar. 31, 2013 SIR	Jul. 09, 2014 SIR Subsequent Event	Mar. 01, 2014 Parent item	Jun. 30, 2014 Amended Agreement	Jun. 06, 2014 RMR	May 08, 2014 RMR	Apr. 07, 2014 RMR	Mar. 07, 2014 RMR	Feb. 07, 2014 RMR	Jan. 31, 2013 RMR	Jun. 30, 2014 RMR item	Jun. 30, 2013 RMR	Jun. 30, 2014 RMR item	Jun. 30, 2013 RMR	Mar. 01, 2014 RMR item	Jul. 09, 2014 RMR Subsequent Event	Jul. 31, 2014 RMR Subsequent Event	Mar. 01, 2014 RMR Parent item	Jun. 30, 2014 RMR Australia	Jun. 30, 2013 RMR Australia	Jun. 30, 2013 RMR Australia	Jun. 30, 2014 RMR Australia	Mar. 15, 2013 GOV	Jun. 30, 2014 GOV	Dec. 31, 2013 GOV	May 09, 2014 AIC	Jun. 30, 2014 AIC item	Jun. 30, 2013 AIC	Jun. 30, 2014 AIC item	Jun. 30, 2013 AIC	May 08, 2014 AIC	Jun. 30, 2014 CWH	Jun. 30, 2014 CWH and an RMR affiliate item	Jun. 02, 2014 Equity Group Investments and associated entities item	Jul. 11, 2014 Related/Corvex	Jun. 10, 2014 Related/Corvex	Jul. 31, 2014 Related/Corvex Subsequent Event	Jul. 11, 2014 Related	Jul. 11, 2014 Corvex
Related person transactions
Term of license agreement																																												1 year
License fee																																												$ 200,000
Number of parking spaces																																												1
Lease term	1 year
Number of renewal options of lease arrangement	1
Renewal term of lease arrangement	3 months
Initial lease payment	200,000
Ownership percentage held by the related party																																													5.70%			2.80%	2.80%
Number of primary agreements																					3		3
Number of entities independent trustees serving as independent directors or independent trustees of other public companies to which related party provides management services																							2
Business management fees																					16,300,000	12,100,000	31,700,000	24,000,000
Portion of shares issued in payment of management fee															11,729	11,275	11,410	10,625	12,187				68,206			10,980
Base business management fee payable in common shares (as a percent)														10.00%													10.00%
Property management and construction supervision fees																					6,800,000	8,600,000	13,800,000	17,000,000
Business and property management fees																													400,000	400,000	800,000	900,000
Payments to MacarthurCook Fund Management Limited																				200,000
Period of prior written notice for termination of either agreement by entity or related party																							60 days
Ownership percentage prior to transaction									100.00%																									100.00%
Realized gain on sale of common shares		(33,000)		(33,000)	66,293,000																												66,300,000
Amount of reimbursements payable to related party		22,984,000		22,984,000		9,385,000	600,000		600,000																										300,000											33,500,000	33,500,000
Less than wholly owned subsidiary, common shares owned							22,000,000		22,000,000		22,000,000
Equity method investments, ownership percentage							36.70%		36.70%																																12.50%
Amount invested in equity investee																																				5,200,000
Number of other companies which are shareholders of related party																																					4		4
Equity investments, common shares sold												22,000,000																					9,950,000			20,000
Price per common share (in dollars per share)												$ 32.04
Equity investments, proceeds from sale												704,800,000																					239,600,000			5,800,000
Coverage amount for property insurance																																					500,000,000		500,000,000
Income (loss) on equity investment		12,454,000	159,000	23,388,000	4,421,000		118,000	79,000	21,000	155,000																											40,000	200,000	(100,000)	300,000
Legal fees and costs																					1,500,000	7,000,000	5,400,000	10,100,000
Number of properties acquired or agreed to be acquired																												1
Number of properties acquired or agreed to be acquired													1												2
Settlement amount																																											12,000,000
Number of installments																																											3
Installment amount receivable on June 30, 2014																																											6,000,000
Each installment amount receivable after first installment																																											3,000,000
Rent due under lease																					$ 1,100,000		$ 1,100,000																			$ 9,200,000