Variable Interest Entities (Details) $ in Thousands	1 Months Ended
	Mar. 31, 2021 USD ($) building item	Dec. 31, 2020 USD ($)
Variable Interest Entity [Line Items]
Assets	$ 6,019,317	$ 6,079,547
Liabilities	$ 2,289,544	2,342,593
Multifamily
Variable Interest Entity [Line Items]
Number of Units in Real Estate Property | building	7,800
JBG Smith, LP
Variable Interest Entity [Line Items]
Ownership interest by parent	90.50%
Unconsolidated VIE
Variable Interest Entity [Line Items]
Assets	$ 116,300	$ 116,200
Variable Interest Entity, Primary Beneficiary
Variable Interest Entity [Line Items]
Assets	5,700
Liabilities	585
Ground lessee equity funding obligation	17,500
Lessee Equity Contribution	9,700
Variable Interest Entity, Primary Beneficiary | Mortgages Payable
Variable Interest Entity [Line Items]
Principal amount	227,000
Proceeds from issuance of mortgage loan	$ 0
Variable Interest Entity, Primary Beneficiary | Mortgages Payable | London Interbank Offered Rate (LIBOR)
Variable Interest Entity [Line Items]
Debt Instrument basis spread on variable rate	3.00%
Variable Interest Entity, Primary Beneficiary | 1900 Crystal Drive | Multifamily
Variable Interest Entity [Line Items]
Number of Units in Real Estate Property | item	808
Number of Towers in Real Estate Property | item	2