Name:	jbgs_BillRentReceivableReserve
Namespace Prefix:	jbgs_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

Amount of credit losses recorded against billed rent receivables during the period due to the effects of an unusual event.

No definition available.

Name:	jbgs_DeferredStraightLineRentReceivablesReserve
Namespace Prefix:	jbgs_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

Amount of lease deferral requests granted during the period due to unusual event.

No definition available.

Name:	jbgs_LeaseDeferralRequestsDueToUnusualEvent
Namespace Prefix:	jbgs_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

Amount of reserves recorded against parking operator receivables during the period.

No definition available.

Name:	jbgs_ParkingOperatorReceivableReserve
Namespace Prefix:	jbgs_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

The percentage of retail tenants revenue from the total revenue.

No definition available.

Name:	jbgs_RetailTenantsRevenuePercent
Namespace Prefix:	jbgs_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

This item represents an other than temporary decline in value that has been recognized against an investment accounted for under the equity method of accounting. The excess of the carrying amount over the fair value of the investment represents the amount of the write down which is or was reflected in earnings. The written down value is a new cost basis with the adjusted value of the investment becoming its new carrying value subject to the equity accounting method. Evidence of a loss in value might include, but would not necessarily be limited to, absence of an ability to recover the carrying amount of the investment or inability of the investee to sustain an earnings capacity which would justify the carrying amount of the investment.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 323
-SubTopic 10
-Section 35
-Paragraph 32
-URI http://asc.fasb.org/extlink&oid=118954474&loc=d3e32787-111569

Name:	us-gaap_EquityMethodInvestmentOtherThanTemporaryImpairment
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

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.

No definition available.