Segment Disclosures (Details 3) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012		Dec. 31, 2011	Dec. 31, 2010
Reconciliation of assets from segment to consolidated
Assets held for sale, net			$ 106,295	$ 147,538
Total assets	19,915,555	[1]	17,408,475	13,331,923
Goodwill	50,346		50,346
Identifiable segment
Reconciliation of assets from segment to consolidated
Gross segment assets	21,058,228		18,410,684	13,108,973
Accumulated depreciation and amortization	(1,978,597)		(1,646,736)	(1,386,850)
Total assets	19,079,631		16,763,948	11,722,123
Senior housing
Reconciliation of assets from segment to consolidated
Gross segment assets	7,658,612		5,785,441	4,196,456
Goodwill	30,500
Post-acute/skilled nursing
Reconciliation of assets from segment to consolidated
Gross segment assets	6,080,826		5,644,472	2,133,640
Goodwill	3,300
Life science
Reconciliation of assets from segment to consolidated
Gross segment assets	3,932,397		3,886,851	3,709,528
Medical office
Reconciliation of assets from segment to consolidated
Gross segment assets	2,661,394		2,336,302	2,299,311
Goodwill	11,400
Hospital
Reconciliation of assets from segment to consolidated
Gross segment assets	724,999		757,618	770,038
Goodwill	5,100
Other non-segment
Reconciliation of assets from segment to consolidated
Total assets	$ 835,924		$ 538,232	$ 1,462,262

[1] The Company's consolidated total assets at December 31, 2012, include assets of certain variable interest entities ("VIEs") that can only be used to settle the liabilities of those VIEs as follows: accounts receivable, net, $1.7 million; cash and cash equivalents, $9.6 million; and other assets, net, $1.8 million. See Note 21 for additional details.