Operating Leases (Details) $ in Millions	3 Months Ended
Mar. 31, 2021 USD ($) property	Mar. 31, 2020 USD ($)
Operating Leases
Number of properties owned	6,662
Percentage rent received \| $	$ 1.0	$ 1.2
Single-client properties
Operating Leases
Number of properties owned	6,621
Single-client properties as percentage of total properties	99.40%
Properties available for lease or sale
Operating Leases
Number of properties owned	131

Amount of operating lease income from variable lease payments paid and payable to lessor, excluding amount included in measurement of lease receivable.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 270
-SubTopic 10
-Section 50
-Paragraph 6A
-URI http://asc.fasb.org/extlink&oid=121640914&loc=SL77927221-108306

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 842
-SubTopic 30
-Section 50
-Paragraph 5
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=121576215&loc=SL77919372-209981

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration