Dispositions (Details) (USD $)	12 Months Ended			1 Months Ended
	Dec. 31, 2014 property	Dec. 31, 2013 property	Dec. 31, 2012	Jun. 30, 2012 property	Dec. 31, 2014 property
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Net gain on the sales of assets	$ 1,213,000	$ 3,617,000	$ 80,952,000
Properties classified as held for sale	50	19			50
Impairment of real estate	56,600,000	51,500,000	35,600,000
Impairment of assets to be disposed of	1,500,000	39,700,000	13,900,000
Triple Net Leased Properties
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Properties classified as held for sale	14	15			14
Senior Living Operations | Seniors Housing Communities
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Operating leases not renewed				2
MOB Operations
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Properties classified as held for sale	36	4			36
MOB Operations | Medical Office Buildings
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Properties classified as held for sale	34				34
Aggregate NOI	11,900,000	13,800,000	14,100,000
2014 Dispositions
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Proceeds from sale of real estate properties including termination fees	118,200,000
Net gain on the sales of assets	1,500,000
Gain from sale of assets	21,300,000
2014 Dispositions | Triple Net Leased Properties
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of real estate properties sold	16				4
Proceeds from sale of real estate properties including termination fees					20,000,000
Impairment of real estate					30,600,000
Disposal group, carrying amount of assets	49,500,000				49,500,000
Disposal group, fair of assets	19,000,000				19,000,000
2014 Dispositions | Senior Living Operations | Seniors Housing Communities
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of real estate properties sold	2
2014 Dispositions | MOB Operations | Medical Office Buildings
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of real estate properties sold	4
2013 Dispositions
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Proceeds from sale of real estate properties including termination fees		35,100,000
Lease termination fees		300,000
Net gain on the sales of assets		5,000,000
2013 Dispositions | Triple Net Leased Properties
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of real estate properties sold		19
2013 Dispositions | Senior Living Operations | Seniors Housing Communities
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of real estate properties sold		1
2013 Dispositions | MOB Operations | Medical Office Buildings
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of real estate properties sold		2
2012 Dispositions
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Proceeds from sale of real estate properties including termination fees			346,100,000
Lease termination fees			5,000,000
Net gain on the sales of assets			$ 85,500,000
2012 Dispositions | Triple Net Leased Properties
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of real estate properties sold			38
2012 Dispositions | Triple Net Leased Properties | Seniors Housing Communities
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of real estate properties sold, tenant purchase option			10
2012 Dispositions | MOB Operations | Medical Office Buildings
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of real estate properties sold			5
Discontinued Operations | Triple Net Leased Properties
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Properties classified as held for sale	3				3
Discontinued Operations | MOB Operations
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Properties classified as held for sale	2				2