Segment Disclosures - Assets (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2015		Dec. 31, 2014
Segment Disclosure
Total assets	$ 21,024,442	[1]	$ 21,369,940	[1]
Goodwill	50,346		50,346
Operating segment
Segment Disclosure
Gross assets	22,743,148		23,042,397
Accumulated depreciation and amortization	(2,680,584)		(2,600,072)
Total assets	20,062,564		20,442,325
Operating segment | Senior housing
Segment Disclosure
Gross assets	8,445,616		8,383,345
Goodwill	31,000		31,000
Operating segment | Post-acute/skilled
Segment Disclosure
Gross assets	6,488,822		6,875,122
Goodwill	3,000		3,000
Operating segment | Life science
Segment Disclosure
Gross assets	4,171,320		4,154,789
Operating segment | Medical office
Segment Disclosure
Gross assets	2,997,583		2,988,888
Goodwill	11,000		11,000
Operating segment | Hospital
Segment Disclosure
Gross assets	639,807		640,253
Goodwill	5,000		5,000
Other non-segment
Segment Disclosure
Total assets	$ 961,878		$ 927,615

[1] The Company’s consolidated total assets at March 31, 2015 and December 31, 2014 include assets of certain variable interest entities (“VIEs”) that can only be used to settle the liabilities of those VIEs. Total assets at March 31, 2015 include VIE assets as follows: buildings and improvements $699 million; land $114 million; accumulated depreciation and amortization $120 million; accounts receivable $15 million; cash $36 million; and other assets, net $14 million. Total assets at December 31, 2014 include VIE assets as follows: buildings and improvements $677 million; land $113 million; accumulated depreciation and amortization $111 million; accounts receivable $5 million; cash $42 million; and other assets, net of $23 million from VIEs. See Note 17 to the Consolidated Financial Statements for additional information.