Real Estate Properties (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended			9 Months Ended			9 Months Ended		1 Months Ended	3 Months Ended	9 Months Ended		3 Months Ended		9 Months Ended			1 Months Ended		9 Months Ended		1 Months Ended	3 Months Ended		1 Months Ended		1 Months Ended							1 Months Ended									1 Months Ended		1 Months Ended		1 Months Ended	3 Months Ended	9 Months Ended	1 Months Ended		1 Months Ended
	Oct. 31, 2012 item	Sep. 30, 2012 item	Sep. 30, 2011 item	Sep. 30, 2012 item	Sep. 30, 2011 item	Dec. 31, 2011	Sep. 30, 2012 Five Star item	Sep. 30, 2012 Sunrise Senior Living, Inc. item	Sep. 30, 2012 Senior living communities Five Star item	Sep. 30, 2012 Senior living communities Sunrise Senior Living, Inc. item	Sep. 30, 2012 Senior living communities Sunrise Senior Living, Inc. item	Oct. 31, 2012 Senior living communities Sunrise Senior Living, Inc. item	Sep. 30, 2011 MOB	Sep. 30, 2012 Acquisition Five Star	Sep. 30, 2012 Acquisition Five Star	Jul. 31, 2012 Acquisition Stellar Senior Living, LLC	Sep. 30, 2012 Operations Transfer Agreement TRS item	Oct. 31, 2012 Operations Transfer Agreement Five Star TRS item	May 31, 2012 Operations Transfer Agreement Five Star TRS item	Sep. 30, 2012 Operations Transfer Agreement Five Star TRS item	Sep. 30, 2012 Operations Transfer Agreement Sunrise Senior Living, Inc. item	May 31, 2012 Operations Transfer Agreement Senior living communities Sunrise Senior Living, Inc. item	Sep. 30, 2012 Operations Transfer Agreement Senior living communities Sunrise Senior Living, Inc.	Feb. 29, 2012 ALABAMA Acquisition Living units item	Feb. 29, 2012 ALABAMA Acquisition Senior living communities	May 31, 2012 South Carolina Acquisition Living units item	May 31, 2012 South Carolina Acquisition Senior living communities	May 31, 2012 South Carolina Acquisition Senior living communities Five Star	May 31, 2012 Georgia Acquisition MOB sqft	May 31, 2012 Georgia Additional acquisition MOB sqft	Jun. 30, 2012 Hawaii Acquisition MOB sqft	Jun. 30, 2012 Maryland Acquisition MOB sqft	Jul. 31, 2012 South Carolina Acquisition Living units item	Jul. 31, 2012 South Carolina Acquisition Senior living communities	Jul. 31, 2012 Texas Acquisition MOB sqft	Sep. 30, 2012 Massachusetts Acquisition MOB sqft	Jul. 31, 2012 Massachusetts Sale MOB sqft item	Jul. 31, 2012 Florida and Minnesota Acquisition MOB sqft	Sep. 30, 2012 Pennsylvania Senior living communities	Dec. 31, 2011 Pennsylvania Senior living communities	Sep. 30, 2012 Pennsylvania Sale Senior living communities item	Jul. 31, 2012 Colorado, Idaho and Washington State Acquisition Living units item	Jul. 31, 2012 Colorado, Idaho and Washington State Acquisition Senior living communities item	Aug. 31, 2012 New York Acquisition Living units item	Aug. 31, 2012 New York Acquisition Senior living communities	Aug. 31, 2012 Missouri Acquisition Living units item	Aug. 31, 2012 Missouri Acquisition Senior living communities	Sep. 30, 2012 Minnesota Acquisition MOB item sqft	Sep. 30, 2012 Minnesota Acquisition MOB item sqft	Aug. 31, 2012 Mississippi, Tennessee and Washington State Acquisition Senior living communities item	Aug. 31, 2012 Mississippi, Tennessee and Washington State Acquisition Senior living communities Living units item	Oct. 31, 2012 Tennessee Acquisition MOB item sqft
Real Estate Properties
Number of properties owned		384		384
Number of states in which properties are located		40		40
Real Estate Properties
Number of properties acquired or agreed to be acquired																																											4					1
Number of units																								92		59							232									511		310		87					437
Number of acquisition agreements	4																																																1	3		1
Aggregate purchase price of properties acquired, excluding closing costs	$ 68,300																								$ 11,300		$ 8,059		$ 8,600	$ 23,100	$ 70,495	$ 18,250		$ 37,273	$ 16,850	$ 16,400		$ 7,750					$ 36,500		$ 99,000		$ 11,280		$ 15,275
Assumption of mortgage notes payable	12,300			112,153	76,931																							4,789			52,000					11,462							6,876		31,187		5,838		9,700
Intangible assets recorded related to acquisition																									583		362						1,762									1,900			2,726		330
Intangible lease assets recorded																													1,392	6,421	4,306	3,570			1,973			789
Fair value of mortgage notes payable																																				12,529						7,488			33,934		6,530
Intangible lease liabilities recorded																													10		629	78
Number of properties acquired, referred as managed properties							30		30
Area of real estate properties acquired (in square feet)																													28,440	111,538	204,429	92,180			63,082	33,600	18,900	52,858										76,637	76,637			33,796
Number of real estate properties leased								2									10					10
Number of properties under accelerated lease termination																					10	10
Number of communities under accelerated lease termination																			10		8
Number of lease communities terminated										3	3	5
Number of lease communities remaining under termination										2
Loss on lease terminations		(104)		(104)						104	104
Rental income		116,281	102,969	336,772	301,839					350	350
Number of communities under management operations																		8	10	10
Payments to purchase the inventory and certain improvements owned by Sunrise				255,769	510,416																		1,000
Number of properties classified as held for sale		1		1																																	1				1
Real estate properties, held for sale		850		850		850																															1,100		850	850
Loss on sale of properties		(101)		(101)	21,315																																101
Impairment of asset charges recorded			1,028	3,071	1,194								1,028
Number of properties impaired			1	1	3
Real estate improvements purchased							18,249							4,156	18,249
Increase or decrease in annual lease rent payable							1,472							335	1,472
Annual lease rent payable																$ 2,920