Organization and Basis of Presentation - Narrative (Details) ft² in Millions, $ in Billions	Sep. 30, 2022 USD ($) ft² property item building
Real Estate Properties [Line Items]
Number of Real Estate Properties	56
National Landing, Northern Virginia
Real Estate Properties [Line Items]
Percentage of operating portfolio by the entity	66.67%
Near-Term Development
Real Estate Properties [Line Items]
Number of Real Estate Properties	8
Area of real estate property \| ft²	3.7
Future Development
Real Estate Properties [Line Items]
Number of Real Estate Properties	16
Area of real estate property \| ft²	8.8
Commercial Real Estate
Real Estate Properties [Line Items]
Number of Real Estate Properties	35
Area of real estate property \| ft²	10.5
One Commercial Building
Real Estate Properties [Line Items]
Number of Units in Real Estate Property \| building	1
Subordinated interest	10.00%
Four Commercial Buildings
Real Estate Properties [Line Items]
Number of Real Estate Properties \| building	4
Subordinated interest	33.50%
Multifamily
Real Estate Properties [Line Items]
Number of Real Estate Properties	19
Number of Units in Real Estate Property \| item	7,359
Multifamily \| Asset under Construction
Real Estate Properties [Line Items]
Number of Real Estate Properties	2
Number of Units in Real Estate Property \| item	1,583
Wholly Owned Properties
Real Estate Properties [Line Items]
Number of properties for ground lease	2
Wholly Owned Properties \| Near-Term Development
Real Estate Properties [Line Items]
Area of real estate property \| ft²	3.5
Wholly Owned Properties \| Future Development
Real Estate Properties [Line Items]
Area of real estate property \| ft²	6.3
Wholly Owned Properties \| Commercial Real Estate
Real Estate Properties [Line Items]
Area of real estate property \| ft²	8.9
Wholly Owned Properties \| Multifamily
Real Estate Properties [Line Items]
Number of Units in Real Estate Property \| item	6,608
Wholly Owned Properties \| Multifamily \| Asset under Construction
Real Estate Properties [Line Items]
Number of Units in Real Estate Property \| item	1,583
Virginia Tech
Real Estate Properties [Line Items]
Under-construction property value developed by Virginia Tech \| $	$ 1
JBG Smith, LP
Real Estate Properties [Line Items]
Ownership interest by parent	88.30%

Percentage of operating portfolio in which the entity serves as the developer.

No definition available.

Name:	jbgs_PercentageOfOperatingPortfolio
Namespace Prefix:	jbgs_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Percentage of subordinated interest held through an unconsolidated real estate venture.

+ References

No definition available.

+ Details

Name:	jbgs_SubordinatedOwnershipInterest
Namespace Prefix:	jbgs_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Value of real estate property being developed by Virginia Tech.

+ References

No definition available.

+ Details

Name:	jbgs_ValueOfRealEstatePropertyBeingDevelopedByVirginiaTech
Namespace Prefix:	jbgs_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Area of a real estate property.

+ References

No definition available.

+ Details

Name:	us-gaap_AreaOfRealEstateProperty
Namespace Prefix:	us-gaap_
Data Type:	dtr-types:areaItemType
Balance Type:	na
Period Type:	instant

- Definition

The parent entity's interest in net assets of the subsidiary, expressed as a percentage.

+ References

No definition available.

+ Details

Name:	us-gaap_MinorityInterestOwnershipPercentageByParent
Namespace Prefix:	us-gaap_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Number of separate real estate development properties located on land subject to ground leases.

+ References

No definition available.

+ Details

Name:	us-gaap_NumberOfPropertiesSubjectToGroundLeases
Namespace Prefix:	us-gaap_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

- Definition

The number of real estate properties owned as of the balance sheet date.

+ References

No definition available.

+ Details

Name:	us-gaap_NumberOfRealEstateProperties
Namespace Prefix:	us-gaap_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

- Definition

The number of units in a real estate property owned as of the balance sheet date.

+ References

No definition available.

+ Details

Name:	us-gaap_NumberOfUnitsInRealEstateProperty
Namespace Prefix:	us-gaap_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

- Definition

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.

+ Details

Name:	us-gaap_RealEstatePropertiesLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Details

Name:	srt_StatementGeographicalAxis=jbgs_NationalLandingVirginiaMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_PropertyPlantAndEquipmentByTypeAxis=jbgs_NearTermDevelopmentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_PropertyPlantAndEquipmentByTypeAxis=jbgs_FutureDevelopmentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis=us-gaap_CommercialRealEstateMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis=jbgs_CommercialRealEstateOneBuildingMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis=jbgs_CommercialRealEstateFourBuildingMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis=srt_MultifamilyMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_PropertyPlantAndEquipmentByTypeAxis=us-gaap_AssetUnderConstructionMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_RealEstatePropertiesAxis=us-gaap_WhollyOwnedPropertiesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	dei_LegalEntityAxis=jbgs_VirginiaTechMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_OwnershipAxis=jbgs_JBGSmithLPMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: