Redeemable Noncontrolling Interests - Narrative (Details) shares in Millions	6 Months Ended
Jun. 30, 2019 shares
JBG Smith, LP
Noncontrolling Interest [Line Items]
Ownership interest by parent	89.80%
Consolidated Real Estate Venture
Noncontrolling Interest [Line Items]
Ownership interest by parent	93.10%
Ownership interest by parent, threshold for capital contributions to cease	97.00%
OP Units [Member]
Noncontrolling Interest [Line Items]
Common shares and OP Units issued in consideration	15.2
Conversion of common limited partnership units to common shares	1.7
OP Units [Member] \| JBG Smith, LP
Noncontrolling Interest [Line Items]
Ownership interest by parent	10.20%
Minimum
Noncontrolling Interest [Line Items]
Redemption period	2 years
Maximum
Noncontrolling Interest [Line Items]
Redemption period	7 years

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Number of shares of equity interests issued or issuable to acquire entity.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 30
-Section 50
-Paragraph 1
-Subparagraph (b)(4)
-URI http://asc.fasb.org/extlink&oid=35744584&loc=d3e6927-128479

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