Dispositions, Assets Held for Sale and Discontinued Operations (Details Textual) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012 properties	Jun. 30, 2011
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Impairment charge	$ 0	$ 0	$ 0	$ 202
Dispositions Assets Held For Sale And Discontinued Operations (Additional Textual) [Abstract]
Numbers of properties sold			23
Gain (loss) on sales of properties	32,450	30,224	33,219	56,380
Deposited in Section 1031 escrow			84,247
Used from Section 1031 escrow			$ 79,300
Seniors Housing Facilities Triple Net [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of real property facilities satisfying held for sale criteria			36
Medical facilities [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of real property facilities satisfying held for sale criteria			0