Real Estate - Acquisitions (Details) - USD ($) $ in Thousands	3 Months Ended
Mar. 31, 2019	Mar. 31, 2018
Real Estate Properties [Line Items]
Acquisitions of real estate assets	$ 109,663	$ 0
Net Lease Asset
Real Estate Properties [Line Items]
Acquisitions of real estate assets	11,500
Leasehold Interest
Real Estate Properties [Line Items]
Acquisitions of real estate assets	$ 98,200
SAFE
Real Estate Properties [Line Items]
Ground lease term (in years)	98 years

The cash outflow from the acquisition of a piece of land, anything permanently fixed to it, including buildings, structures on it and so forth; includes real estate intended to generate income for the owner; excludes real estate acquired for use by the owner.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 13
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=109223946&loc=d3e3213-108585

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