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Term of lessor's operating lease, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 842
-SubTopic 30
-Section 50
-Paragraph 3
-Subparagraph (a)(3)
-URI http://asc.fasb.org/extlink&oid=77888428&loc=SL77919359-209981

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- Definition

The cash outflow from the acquisition of real estate intended to generate income for the owner; excludes land acquired for use by the owner.

+ References

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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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.

+ References

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

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Real Estate (Acquisitions) (Details) $ in Thousands	1 Months Ended	3 Months Ended	12 Months Ended
Real Estate (Acquisitions) (Details) $ in Thousands	Apr. 30, 2017 property	Sep. 30, 2017 USD ($) lease	Dec. 31, 2018 USD ($) lease_asset	Dec. 31, 2017 USD ($) lease_asset	Dec. 31, 2016 USD ($) lease_asset property
Real Estate Properties [Line Items]
Number of net lease assets \| lease_asset			2	1	1
Acquisitions of real estate assets			$ 19,454	$ 6,600	$ 38,433
Payments for land and funded tenant improvements					$ 3,900
Number of properties \| property					2
Net Lease Asset
Real Estate Properties [Line Items]
Acquisitions of real estate assets			$ 14,800	$ 6,600	$ 32,700
Fair value in excess of carrying value		$ 1,500
Operating leases, term (in years)					99 years
Ground Net Lease Business \| Safety, Income and Growth, Inc.
Real Estate Properties [Line Items]
Number of properties \| property	12
Master Lease
Real Estate Properties [Line Items]
Number of leases modified \| lease		2