Dispositions, Assets Held for Sale and Discontinued Operations (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011
Real property dispositions:
Total dispositions			$ 123,470	$ 152,312
Gain (loss) on sales of properties	32,450	30,224	33,219	56,380
Proceeds from sales of real property			156,689	208,692
Revenues:
Rental income	9,833	15,943	20,040	32,242
Expenses:
Interest expense	1,794	3,289	3,543	6,490
Property operating expenses	10	1,219	436	2,970
Provision for depreciation	1,046	3,798	3,564	8,882
Income (loss) from discontinued operations, net	6,983	7,637	12,497	13,900
Seniors Housing Facilities Triple Net [Member]
Real property dispositions:
Total dispositions			90,404	117,074
Medical facilities [Member]
Real property dispositions:
Total dispositions			$ 33,066	$ 35,238