Real Estate Properties (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended	9 Months Ended		12 Months Ended	5 Months Ended	9 Months Ended	1 Months Ended					9 Months Ended	1 Months Ended				1 Months Ended	5 Months Ended		5 Months Ended	1 Months Ended					9 Months Ended		12 Months Ended	3 Months Ended	9 Months Ended	12 Months Ended
	Sep. 30, 2011 property segment Y count state	Sep. 30, 2011 property segment Y count state	Sep. 30, 2010 property	Dec. 31, 2010 property	Sep. 30, 2011 Acquisition sqft agreement	Sep. 30, 2011 Acquisition	Aug. 31, 2011 Acquisition Five States in the southeastern United States Senior living communities property	Jul. 31, 2011 Acquisition Five States in the southeastern United States Senior living communities property	Jun. 30, 2011 Acquisition Five States in the southeastern United States Senior living communities property	May 31, 2011 Acquisition Five States in the southeastern United States Senior living communities property	Mar. 31, 2011 Acquisition Five States in the southeastern United States Senior living communities property state	Sep. 30, 2011 Acquisition Five States in the southeastern United States Senior living communities property	Jul. 31, 2011 Acquisition Alachua, Florida Medical Office Building property sqft	Sep. 30, 2011 Acquisition Six States Senior living communities state	Jul. 31, 2011 Acquisition Six States Senior living communities Five Star property	Sep. 30, 2011 Acquisition Six States Senior living communities Living units property	Sep. 30, 2011 Acquisition Six States Senior living communities TRS property	Sep. 30, 2011 Acquisition Senior living communities property	Jun. 30, 2011 Acquisition Senior living communities Five Star property	Sep. 30, 2011 Acquisition Medical Office Building property	Sep. 30, 2011 Acquisition Medical Office Building CommonWealth REIT (CWH) sqft property state	Aug. 31, 2011 Acquisition Land for future development acre	Jul. 31, 2011 Acquisition Land for future development	Sep. 30, 2011 Acquisition Assisted living community property	Sep. 30, 2011 Pennsylvania unit property	Sep. 30, 2011 Senior living communities property	Sep. 30, 2011 Medical Office Building property	Dec. 31, 2010 Medical Office Building property	Sep. 30, 2011 Five Star	Sep. 30, 2011 Five Star	Dec. 31, 2010 Five Star
Real estate properties
Number of properties owned	357	357
Number of states in which properties are located	37	37									5			6							8
Number of properties agreed to be acquired											20	2	1					1		3	13
Aggregate purchase price of properties acquired, excluding closing costs					$ 43,725	$ 569,893	$ 17,158	$ 44,671	$ 196,594		$ 304,000		$ 5,200	$ 478,000							$ 167,000	$ 4,000						$ 433,955
Number of properties acquired							1	3	14																	19	25	26
Mortgage loans assumed in real estate acquisition	28,869	(76,931)	(2,458)				12,459	12,757	48,062														3,653
Mortgage loans expected to be assumed in real estate acquisition					9,700	9,700								164,000
Number of properties classified as held for sale																									1
Number of units in real estate property held for sale	1	1																							103
Real estate properties, held for sale	166	166																							850
Number of acquisition agreements					3
Number of properties agreed to be acquired, referred as managed properties										15					9
Number of properties agreed to be acquired, referred as leased properties										5							8
Number of properties acquired, referred as managed properties							1	2	10
Number of real estate properties leased																			4
Number of units																2,226								57
Area of real estate properties acquired (in square feet)					138,606								32,476								1,300,000
Intangible lease assets recorded													354								31,150
Intangible lease liabilities recorded																					1,919
Area of real estate property acquired (in acres)																						47
Impairment of assets charges recorded	1,028	1,194	1,095	5,965
Number of properties impaired	1	3	5	7
Real estate improvements purchased																													10,554	25,877	31,894
Increase or decrease in annual lease rent payable																													$ 845	$ 2,073