Segment Reporting - Segment Assets (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Segment Reporting Information, Additional Information
Assets	$ 2,356,797	$ 2,330,997
Net Lease
Segment Reporting Information, Additional Information
Assets	1,524,949	1,572,437
Self Storage
Segment Reporting Information, Additional Information
Assets	392,273	398,944
Multi-family
Segment Reporting Information, Additional Information
Assets	297,276	256,875
Corporate
Segment Reporting Information, Additional Information
Assets	77,859	35,812
All Other
Segment Reporting Information, Additional Information
Assets	$ 64,440	$ 66,929

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