Dispositions, Assets Held for Sale and Discontinued Operations (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Real property dispositions:
Total dispositions			$ 256,331	$ 165,020
Gain (loss) on sales of properties, net	12,827	185	46,046	56,565
Proceeds from sales of real property			302,377	221,585
Revenues:
Rental income	8,441	14,147	33,287	51,117
Expenses:
Interest expense	1,663	3,382	6,669	11,387
Property operating expenses	219	944	1,099	4,331
Provision for depreciation	708	4,058	6,190	14,838
Income (loss) from discontinued operations, net	5,851	5,763	19,329	20,561
Seniors Housing Facilities Triple Net [Member]
Real property dispositions:
Total dispositions			149,984	129,725
Medical facilities [Member]
Real property dispositions:
Total dispositions			$ 106,347	$ 35,295