Dispositions, Assets Held for Sale and Discontinued Operations (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2012	Mar. 31, 2011
Real property dispositions:
Total dispositions	$ 31,815	$ 17,892
Gain (loss) on sales of properties	769	26,156
Proceeds from sales of real property	32,584	44,048
Revenues:
Rental income	5,991	12,125
Expenses:
Interest expense	1,010	2,428
Property operating expenses	426	1,751
Provision for depreciation	1,467	4,025
Income (loss) from discontinued operations, net	3,088	3,921
Seniors housing triple-net [Member]
Real property dispositions:
Total dispositions	0	17,892
Medical facilities [Member]
Real property dispositions:
Total dispositions	$ 31,815	$ 0