Related Person Transactions (Details) (USD $)	3 Months Ended					3 Months Ended			3 Months Ended		1 Months Ended		3 Months Ended		1 Months Ended			3 Months Ended					1 Months Ended
	Mar. 31, 2014 item property	Mar. 31, 2013	Apr. 30, 2014 item	Mar. 31, 2014 Senior living communities item	Dec. 31, 2013 Senior living communities item	Mar. 31, 2014 Five Star item	Mar. 31, 2013 Five Star	Dec. 31, 2001 Five Star	Mar. 31, 2014 Five Star AL Pooling Agreement item	Mar. 31, 2014 Five Star IL Pooling Agreement item	Aug. 31, 2013 Five Star Senior living communities property item	Jun. 30, 2013 Five Star Senior living communities property	Mar. 31, 2014 Five Star Senior living communities item	Mar. 31, 2014 Five Star Acquisition Senior living communities New York item	Jan. 31, 2014 Five Star Sale Senior living communities property item	Aug. 31, 2013 Five Star Sale Senior living communities item	Jan. 31, 2014 Five Star Sale Senior living communities Texas item	Mar. 31, 2014 RMR item	Mar. 31, 2013 RMR	Mar. 31, 2014 AIC	Mar. 31, 2013 AIC	Dec. 31, 2013 AIC	Apr. 30, 2014 AIC Subsequent event
Related person transactions
Beneficial ownership of common shares (as a percent)								100.00%
Investment in common shares						4,235,000
Percentage of total shares outstanding						8.70%
Number of real estate properties leased													186
Minimum annual rent payable to entity						$ 190,614,000
Total rental income recognized						47,506,000	49,444,000
Rents receivable						15,835,000	17,620,000
Deferred estimated percentage rent						1,416,000	1,254,000
Real estate improvements purchased						8,614,000	8,171,000
Increase or decrease in annual lease rent payable						689,000	654,000				255,000				210,000
Number of properties agreed to be offered for sale	13			9	10						10		9
Sale price of properties under agreement to be sold															2,400,000	2,550,000	2,400,000
Number of properties sold or agreed to be sold											1				1		36
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%				8.75%
Number of combination or pooling agreements						4			3
Number of communities that include assisted living units									20
Number of communities that include independent living units										2
Number of properties acquired, referred to as managed properties													44
Property management agreement expense						2,425,000	2,295,000											1,638,000	1,600,000
Number of living units				708	744									310	36	112
Number of employees	0
Number of agreements to avail management and administrative services																		2
Number of Managing Trustees also serving as managing trustee of Five Star						1
Business management agreement expense																		6,682,000	6,550,000
Common shares issued as payment for base business management fee																		30,279
Base business management fee payable in common shares (as a percent)																		10.00%
Number of other shareholders in the equity method investee company	4		6
Ownership percentage held by the entity and other shareholders																				14.30%			14.30%
The entity owns less than this percentage of an equity method investment																				20.00%
Amount invested in equity investee																				5,209,000
Equity method investments, carrying value																				5,835,000		5,913,000
Earnings and losses recognized arising from equity investments	(97,000)	76,000																		(97,000)	76,000
Coverage of property insurance																				500,000,000
Number of shares purchased																							2,857
Payments for share purchased																							$ 825,000,000