Debt - Revolving Credit Facility and Term Loans (Details) $ in Millions	12 Months Ended
Dec. 31, 2025 USD ($) Option	Dec. 31, 2024 USD ($)
Debt
Debt Instrument, Variable Interest Rate, Type [Extensible Enumeration]	Secured Overnight Financing Rate (SOFR) [Member]
Line of credit
Debt
Credit facility, maximum borrowing capacity	$ 1,500.0	$ 1,500.0
Line of credit \| Revolving credit facility
Debt
Credit facility, maximum borrowing capacity	$ 750.0	750.0
Number of extension options \| Option	2
Extension period	6 months
Line of credit \| Revolving credit facility \| Daily SOFR \| Minimum
Debt
Basis spread on variable rate (in percent)	1.40%
Line of credit \| Revolving credit facility \| Daily SOFR \| Maximum
Debt
Basis spread on variable rate (in percent)	1.85%
Line of credit \| Tranche A-1 Term Loan
Debt
Credit facility, maximum borrowing capacity	$ 200.0	200.0
Line of credit \| Tranche A-1 Term Loan \| One-Month Term SOFR \| Minimum
Debt
Basis spread on variable rate (in percent)	1.15%
Line of credit \| Tranche A-1 Term Loan \| One-Month Term SOFR \| Maximum
Debt
Basis spread on variable rate (in percent)	1.75%
Line of credit \| Tranche A-2 Term Loan
Debt
Credit facility, maximum borrowing capacity	$ 400.0	400.0
Line of credit \| Tranche A-2 Term Loan \| One-Month Term SOFR \| Minimum
Debt
Basis spread on variable rate (in percent)	1.25%
Line of credit \| Tranche A-2 Term Loan \| One-Month Term SOFR \| Maximum
Debt
Basis spread on variable rate (in percent)	1.80%
Line of credit \| 2023 Term Loan
Debt
Credit facility, maximum borrowing capacity	$ 120.0	$ 120.0
Line of credit \| 2023 Term Loan \| One-Month Term SOFR \| Minimum
Debt
Basis spread on variable rate (in percent)	1.25%
Line of credit \| 2023 Term Loan \| One-Month Term SOFR \| Maximum
Debt
Basis spread on variable rate (in percent)	1.80%
Line of credit \| Term Loans \| Maximum
Debt
Additional borrowing capacity	$ 500.0

Debt Instrument, Extension Period

No definition available.

Name:	jbgs_DebtInstrumentExtensionPeriod
Namespace Prefix:	jbgs_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Debt Instrument, Number Of Term Extension Options

+ References

No definition available.

+ Details

Name:	jbgs_DebtInstrumentNumberOfTermExtensionOptions
Namespace Prefix:	jbgs_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

- Definition

Additional borrowing capacity under the credit facility without consideration of any current restrictions on the amount that could be borrowed or the amounts currently outstanding under the facility.

+ References

No definition available.

+ Details

Name:	jbgs_LineOfCreditAdditionalBorrowingCapacity
Namespace Prefix:	jbgs_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Percentage points added to the reference rate to compute the variable rate on the debt instrument.

+ References

No definition available.

+ Details

Name:	us-gaap_DebtInstrumentBasisSpreadOnVariableRate1
Namespace Prefix:	us-gaap_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Indicates type of variable interest rate on debt instrument.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 942
-SubTopic 470
-Name Accounting Standards Codification
-Section 50
-Paragraph 3
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147477734/942-470-50-3

+ Details

Name:	us-gaap_DebtInstrumentVariableInterestRateTypeExtensibleEnumeration
Namespace Prefix:	us-gaap_
Data Type:	enum2:enumerationSetItemType
Balance Type:	na
Period Type:	duration

- 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

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 235
-SubTopic 10
-Name Accounting Standards Codification
-Section S50
-Paragraph 1
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480738/235-10-S50-1

Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 235
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08(f))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480678/235-10-S99-1

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 6
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481544/470-10-50-6

Reference 4: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 470
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 6
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481544/470-10-50-6

+ Details

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

- Definition

Maximum borrowing capacity under the credit facility without consideration of any current restrictions on the amount that could be borrowed or the amounts currently outstanding under the facility.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Topic 210
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(22)(b))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480566/210-10-S99-1

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Topic 210
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(19)(b))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480566/210-10-S99-1

+ Details

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

- Details

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Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

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Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

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Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_RangeAxis=srt_MinimumMember
Namespace Prefix:
Data Type:	na
Balance Type:
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- Details

Name:	srt_RangeAxis=srt_MaximumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

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Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_VariableRateAxis=jbgs_OneMonthTermSecuredOvernightFinancingRateMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

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Namespace Prefix:
Data Type:	na
Balance Type:
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- Details

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Namespace Prefix:
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- Details

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Namespace Prefix:
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