Related Person Transactions (Details) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended		9 Months Ended					1 Months Ended	0 Months Ended	1 Months Ended	3 Months Ended		9 Months Ended		1 Months Ended		3 Months Ended		9 Months Ended				9 Months Ended		1 Months Ended			3 Months Ended	9 Months Ended		1 Months Ended				1 Months Ended			3 Months Ended		9 Months Ended
	Sep. 30, 2013 item	Sep. 30, 2012	Sep. 30, 2013 item	Sep. 30, 2012	Sep. 30, 2013 Senior living communities item	Dec. 31, 2012 Senior living communities item	Sep. 30, 2013 Rehabilitation hospitals item	Aug. 31, 2013 Purchase Agreement Rehabilitation hospitals item	Mar. 27, 2013 RMR	Jul. 31, 2013 RMR item	Sep. 30, 2013 RMR item	Oct. 01, 2012 RMR	Sep. 30, 2013 RMR item	Sep. 30, 2012 RMR	Sep. 30, 2013 Five Star item	Apr. 30, 2012 Five Star	Sep. 30, 2013 Five Star item	Sep. 30, 2012 Five Star	Sep. 30, 2013 Five Star item	Sep. 30, 2012 Five Star	Dec. 31, 2012 Five Star	May 31, 2011 Five Star	Sep. 30, 2013 Five Star AL Pooling Agreement item	Sep. 30, 2013 Five Star Second AL Pooling Agreement item	Aug. 31, 2012 Five Star IL Pooling Agreement item	Aug. 31, 2013 Five Star Senior living communities item	May 31, 2011 Five Star Senior living communities item	Oct. 31, 2013 Five Star Senior living communities item	Sep. 30, 2013 Five Star Senior living communities item	Sep. 30, 2013 Five Star Rehabilitation hospitals item	Oct. 31, 2013 Five Star Acquisition Senior living communities item	Oct. 31, 2013 Five Star Acquisition Senior living communities GA item	Aug. 31, 2013 Five Star Acquisition Senior living communities GA Cumming item	Sep. 30, 2013 Five Star Acquisition Senior living communities New York item	Oct. 31, 2013 Five Star Acquisition Senior living communities TN item	Aug. 31, 2013 Five Star Sale Senior living communities item	Jun. 30, 2013 AIC	Sep. 30, 2013 AIC	Sep. 30, 2012 AIC	Sep. 30, 2013 AIC	Sep. 30, 2012 AIC	Dec. 31, 2012 AIC
Related person transactions
Beneficial ownership of common shares (as a percent)															100.00%		100.00%		100.00%
Investment in common shares															4,235,000		4,235,000		4,235,000
Percentage of total shares outstanding															8.80%		8.80%		8.80%
Number of real estate properties leased																													187	2
Minimum annual rent payable to entity																			$ 199,257
Total rental income recognized																	49,705	49,148	148,732	146,901
Rents receivable															17,863		17,863		17,863		17,680
Deferred percentage rent																	1,301	1,190	3,823	3,602
Real estate improvements purchased																			22,501
Increase or decrease in annual lease rent payable															9,500				1,800							255
Sale price of properties under agreement to be sold								90,000																												2,550
Number of properties sold or agreed to be sold								2																		1
Number of properties agreed to be sold																													11
Increase or decrease in annual lease rent payable as a percentage of net proceeds of the sale																										10.00%
Number of properties agreed to be offered for sale	19		19		10	1	2																			10
Number of combination or pooling agreements															3		3		3				2
Number of communities that include assisted living units																							20								3
Number of communities that include independent living units																									2							2			1
Number of properties acquired, referred to as managed properties																												4	40
Property management agreement expense											1,678	1,557	4,937	4,328			2,290	1,284	6,866	3,431
Number of living units					744	120	364																	3							213		93	310		112
Aggregate purchase price of properties acquired, excluding closing costs																															29,100		22,030
Amount agreed to be lent under Bridge Loan Agreement																						80,000
Number of employees	0		0
Number of agreements to avail management and administrative services											2		2
Number of Managing Trustees also serving as managing trustee of Five Star															1		1		1
Business management agreement expense											6,847	6,745	20,088	19,472
Common shares issued in payment of an incentive fee for services rendered from RMR									21,968
Base business management fee payable in common shares (as a percent)											10.00%		10.00%
Management fees payable under property management agreement as a percentage of gross rents																													5.00%
Interest and other income	42	248	612	957																314
Proceeds from repayment of bridge loan																38,000
Number of other shareholders in the equity method investee company	5		5
Ownership percentage held by us, RMR, Five Star, CWH and four other companies																																						12.50%		12.50%
The entity owns less than this percentage of an equity method investment																																						20.00%		20.00%
Number of properties acquired or agreed to be acquired																											6
Amount invested in equity investee																																						5,209		5,209
Equity method investments, carrying value																																						5,781		5,781		5,629
Earnings and losses recognized arising from equity investments	64	115	219	236																																		64	115	219	236
Period for which property insurance program was extended																																					1 year
Coverage of property insurance																																								500,000
Total premiums including taxes and fees																																					4,748
Incentive fee payable																													0
Number of entities to which RMR provides management services										4
Aggregate coverage of combined directors' and officers' liability insurance policy purchased by the related party										10,000
Aggregate coverage of separate directors' and officers' liability insurance policy purchased										5,000
Premium paid for combined and separate directors' and officers' liability insurance policy										$ 343