Segment Information (Assets) (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Assets
Total assets	$ 22,584,555	$ 23,954,541
Percentage of total assets	100.00%	100.00%
Operating Segments \| Triple Net Leased Properties
Assets
Total assets	$ 6,795,142	$ 7,778,064
Percentage of total assets	30.10%	32.40%
Operating Segments \| Senior Living Operations
Assets
Total assets	$ 8,156,187	$ 7,654,609
Percentage of total assets	36.10%	32.00%
Operating Segments \| Office Operations
Assets
Total assets	$ 6,772,957	$ 6,897,696
Percentage of total assets	30.00%	28.80%
All Other
Assets
Total assets	$ 860,269	$ 1,624,172
Percentage of total assets	3.80%	6.80%

Sum of the carrying amounts as of the balance sheet date of all assets that are recognized. Assets are probable future economic benefits obtained or controlled by an entity as a result of past transactions or events.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03(11))
-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 22
-URI http://asc.fasb.org/extlink&oid=115929826&loc=d3e8736-108599

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03(a)(12))
-URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910

Name:	us-gaap_Assets
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant