Real Property Acquisitions and Development (Details 2) (USD $) In Thousands, unless otherwise specified	6 Months Ended
	Jun. 30, 2011	Jun. 30, 2010
Real property acquisitions:
Properties	218	29
Amount	$ 4,048,102	$ 356,074
Less: Assumed debt	(721,632)	(117,892)
Assumed other items, net	(147,500)	(31,690)
Cash disbursed for acquisitions	3,178,970	206,492
Construction in progress additions:
Amount	200,149	180,294
Less: Capitalized interest	(6,979)	(11,983)
Accruals	(30,736)	(5,775)
Cash disbursed for construction in progress	162,434	162,536
Capital improvements to existing properties	29,193	20,845
Total cash invested in real property	3,370,597	389,873
Development projects:
Total development projects	325,563	379,741
Expansion projects	19,218	1,502
Total construction in progress conversions	344,781	381,243
Senior housing operating [Member]
Real property acquisitions:
Properties	46
Amount	1,126,130
Senior housing triple-net [Member]
Real property acquisitions:
Properties	165	10
Amount	2,849,603	109,492
Construction in progress additions:
Amount	75,999	50,726
Development projects:
Total development projects		269,260
Land parcels [Member]
Real property acquisitions:
Properties	1
Amount	6,770
Medical facilities [Member]
Real property acquisitions:
Properties	6	19
Amount	65,599	246,582
Construction in progress additions:
Amount	124,150	129,568
Development projects:
Total development projects	$ 325,563	$ 110,481