Transactions with Vornado and Related Parties	12 Months Ended
Dec. 31, 2018
Related Party Transactions [Abstract]
Related Party Transactions Disclosure [Text Block]	Transactions with Vornado and Related Parties Transactions with Vornado As described in Note 1, the accompanying financial statements present the operations of the Vornado Included Assets as carved-out from the financial statements of Vornado for all periods prior to July 17, 2017. Certain centralized corporate costs borne by Vornado for management and other services including, but not limited to, accounting, reporting, legal, tax, information technology and human resources have been allocated to the assets in the financial statements based on either actual costs incurred or a proportion of costs estimated to be applicable to the Vornado Included Assets based on key metrics including total revenue. The total amounts allocated during the years ended December 31, 2017 and 2016 were $13.0 million and $20.7 million. These allocated amounts are included as a component of "General and administrative expense: Corporate and other" expenses on the statements of operations and do not necessarily reflect what actual costs would have been if the Vornado Included Assets were a separate standalone public company. In connection with the Formation Transaction, we entered into an agreement with Vornado under which Vornado provides operational support for an initial period of up to two years. These services include information technology, financial reporting and payroll services. The charges for these services are based on an hourly or per transaction fee arrangement including reimbursement for overhead and out-of-pocket expenses. The total charges for the years ended December 31, 2018 and 2017 were $3.6 million and $2.2 million. Pursuant to an agreement, we are providing Vornado with leasing and property management services for certain of its assets that were not part of the Separation. The total revenue related to these services for the years ended December 31, 2018 and 2017 were $2.1 million and $779,000. We believe that the terms of both of these agreements are comparable to those that would have been negotiated based on market rates. In connection with the Formation Transaction, we entered into a Tax Matters Agreement with Vornado. See Note 19 for additional information. In August 2014, we completed a $185.0 million financing of the Universal Buildings, a 687,000 square foot office complex located in Washington, D.C. In connection with this financing, pursuant to a note agreement dated August 12, 2014, we used a portion of the financing proceeds and made an $86.0 million loan to Vornado at LIBOR plus 2.9% due August 2019. At the Separation, Vornado repaid the outstanding balance of the loan and related accrued interest. We recognized interest income of $1.8 million and $3.3 million during the years ended December 31, 2017 and 2016. In connection with the development of The Bartlett, prior to the Separation, we entered into various note agreements with Vornado whereby we could borrow up to a maximum of $170.0 million. Vornado contributed these note agreements along with accrued and unpaid interest to JBG SMITH at the Separation. We incurred interest expense of $4.1 million during each of the years ended December 31, 2017 and 2016. In June 2016, the $115.0 million mortgage loan (including $608,000 of accrued interest) secured by the Bowen Building, a 231,000 square foot office building located in Washington, D.C., was repaid with the proceeds of a $115.6 million draw on our former parent's revolving credit facility. We repaid our former parent with amounts drawn under our revolving credit facility at the Combination. We incurred interest expense related to the mortgage loan of $1.3 million and $1.1 million during the years ended December 31, 2017 and 2016. We have agreements that are terminable on the second anniversary of the Combination with Building Maintenance Services ("BMS"), a wholly owned subsidiary of Vornado, to supervise cleaning, engineering and security services at our properties. We paid BMS $20.9 million, $13.6 million and $12.1 million during each of the three years in the period ended December 31, 2018, which are included in "Property operating expenses" in our statements of operations. We entered into a consulting agreement with Mitchell Schear, a member of our Board of Trustees and formerly the president of Vornado’s Washington, D.C. segment. The consulting agreement expired on December 31, 2017 and provided for the payment of consulting fees and expenses at the rate of $169,400 per month for the 24 months following the Separation, including after the expiration of the consulting agreement. The amount due under this consulting agreement of $4.1 million was expensed in connection with the Combination. As of December 31, 2018, the remaining liability is $1.1 million. Additionally, in March 2017, Vornado amended Mr. Schear’s employment agreement to provide for the payment of severance, bonus and post-employment services. A total of $16.4 million was expensed in connection with the Separation during the year ended December 31, 2017. Transactions with Real Estate Ventures Our third-party asset management and real estate services business provides fee-based real estate services to third parties and the JBG Legacy Funds. We provide services for the benefit of the JBG Legacy Funds that own interests in the assets retained by the JBG Legacy Funds. In connection with the contribution of the JBG Assets to us, it was determined that the general partner and managing member interests in the JBG Legacy Funds that were held by former JBG executives (and who became members of our management team and/or Board of Trustees) would not be transferred to us and remain under the control of these individuals. In addition, certain members of our senior management and Board of Trustees have an ownership interest in the JBG Legacy Funds and own carried interests in each fund and in certain of our real estate ventures that entitles them to receive additional compensation if the fund or real estate venture achieves certain return thresholds. This third-party real estate services revenue, including reimbursements, from these JBG Legacy Funds for the years ended December 31, 2018 and 2017 was $33.8 million and $19.9 million. As of December 31, 2018 and 2017, we had receivables from the JBG Legacy Funds totaling $3.6 million and $3.1 million for third-party real estate services, including reimbursements. We rent our corporate offices from an unconsolidated real estate venture and incurred expenses totaling $4.9 million and $2.3 million during the years ended December 31, 2018 and 2017, which is recorded in "General and administrative expense: Corporate and other" in our statements of operations. Registration Rights Agreements In connection with the Formation Transaction, we entered into a registration rights agreement with certain former investors in the JBG Legacy Funds that received our common shares in the Formation Transaction (the "Shares Registration Rights Agreement") and a separate registration rights agreement with the certain former investors in the JBG Legacy Funds and certain employees of JBG entities that received OP Units in the Formation Transaction (the "OP Units Registration Rights Agreement" and together with the Shares Registration Rights Agreement, the "Registration Rights Agreements"). Certain holders of common shares and OP Units who may benefit from the Registration Rights Agreements are members of our management team and/or Board of Trustees. Our obligations under the Shares Registration Rights Agreement were fully satisfied in January 2018.

Transactions with Vornado and Related Parties

Transactions with Vornado

As described in Note 1, the accompanying financial statements present the operations of the Vornado Included Assets as carved-out from the financial statements of Vornado for all periods prior to July 17, 2017.

Certain centralized corporate costs borne by Vornado for management and other services including, but not limited to, accounting, reporting, legal, tax, information technology and human resources have been allocated to the assets in the financial statements based on either actual costs incurred or a proportion of costs estimated to be applicable to the Vornado Included Assets based on key metrics including total revenue. The total amounts allocated during the years ended December 31, 2017 and 2016 were $13.0 million and $20.7 million. These allocated amounts are included as a component of "General and administrative expense: Corporate and other" expenses on the statements of operations and do not necessarily reflect what actual costs would have been if the Vornado Included Assets were a separate standalone public company.

In connection with the Formation Transaction, we entered into an agreement with Vornado under which Vornado provides operational support for an initial period of up to two years. These services include information technology, financial reporting and payroll services. The charges for these services are based on an hourly or per transaction fee arrangement including reimbursement for overhead and out-of-pocket expenses. The total charges for the years ended December 31, 2018 and 2017 were $3.6 million and $2.2 million. Pursuant to an agreement, we are providing Vornado with leasing and property management services for certain of its assets that were not part of the Separation. The total revenue related to these services for the years ended December 31, 2018 and 2017 were $2.1 million and $779,000. We believe that the terms of both of these agreements are comparable to those that would have been negotiated based on market rates.

In connection with the Formation Transaction, we entered into a Tax Matters Agreement with Vornado. See Note 19 for additional information.

In August 2014, we completed a $185.0 million financing of the Universal Buildings, a 687,000 square foot office complex located in Washington, D.C. In connection with this financing, pursuant to a note agreement dated August 12, 2014, we used a portion of the financing proceeds and made an $86.0 million loan to Vornado at LIBOR plus 2.9% due August 2019. At the Separation, Vornado repaid the outstanding balance of the loan and related accrued interest. We recognized interest income of $1.8 million and $3.3 million during the years ended December 31, 2017 and 2016.

In connection with the development of The Bartlett, prior to the Separation, we entered into various note agreements with Vornado whereby we could borrow up to a maximum of $170.0 million. Vornado contributed these note agreements along with accrued and unpaid interest to JBG SMITH at the Separation. We incurred interest expense of $4.1 million during each of the years ended December 31, 2017 and 2016.

In June 2016, the $115.0 million mortgage loan (including $608,000 of accrued interest) secured by the Bowen Building, a 231,000 square foot office building located in Washington, D.C., was repaid with the proceeds of a $115.6 million draw on our former parent's revolving credit facility. We repaid our former parent with amounts drawn under our revolving credit facility at the Combination. We incurred interest expense related to the mortgage loan of $1.3 million and $1.1 million during the years ended December 31, 2017 and 2016.

We have agreements that are terminable on the second anniversary of the Combination with Building Maintenance Services ("BMS"), a wholly owned subsidiary of Vornado, to supervise cleaning, engineering and security services at our properties. We paid BMS $20.9 million, $13.6 million and $12.1 million during each of the three years in the period ended December 31, 2018, which are included in "Property operating expenses" in our statements of operations.

We entered into a consulting agreement with Mitchell Schear, a member of our Board of Trustees and formerly the president of Vornado’s Washington, D.C. segment. The consulting agreement expired on December 31, 2017 and provided for the payment of consulting fees and expenses at the rate of $169,400 per month for the 24 months following the Separation, including after the expiration of the consulting agreement. The amount due under this consulting agreement of $4.1 million was expensed in connection with the Combination. As of December 31, 2018, the remaining liability is $1.1 million. Additionally, in March 2017, Vornado amended Mr. Schear’s employment agreement to provide for the payment of severance, bonus and post-employment services. A total of $16.4 million was expensed in connection with the Separation during the year ended December 31, 2017.

Transactions with Real Estate Ventures

Our third-party asset management and real estate services business provides fee-based real estate services to third parties and the JBG Legacy Funds. We provide services for the benefit of the JBG Legacy Funds that own interests in the assets retained by the JBG Legacy Funds. In connection with the contribution of the JBG Assets to us, it was determined that the general partner and managing member interests in the JBG Legacy Funds that were held by former JBG executives (and who became members of our management team and/or Board of Trustees) would not be transferred to us and remain under the control of these individuals. In addition, certain members of our senior management and Board of Trustees have an ownership interest in the JBG Legacy Funds and own carried interests in each fund and in certain of our real estate ventures that entitles them to receive additional compensation if the fund or real estate venture achieves certain return thresholds. This third-party real estate services revenue, including reimbursements, from these JBG Legacy Funds for the years ended December 31, 2018 and 2017 was $33.8 million and $19.9 million. As of December 31, 2018 and 2017, we had receivables from the JBG Legacy Funds totaling $3.6 million and $3.1 million for third-party real estate services, including reimbursements.

We rent our corporate offices from an unconsolidated real estate venture and incurred expenses totaling $4.9 million and $2.3 million during the years ended December 31, 2018 and 2017, which is recorded in "General and administrative expense: Corporate and other" in our statements of operations.

Registration Rights Agreements

In connection with the Formation Transaction, we entered into a registration rights agreement with certain former investors in the JBG Legacy Funds that received our common shares in the Formation Transaction (the "Shares Registration Rights Agreement") and a separate registration rights agreement with the certain former investors in the JBG Legacy Funds and certain employees of JBG entities that received OP Units in the Formation Transaction (the "OP Units Registration Rights Agreement" and together with the Shares Registration Rights Agreement, the "Registration Rights Agreements"). Certain holders of common shares and OP Units who may benefit from the Registration Rights Agreements are members of our management team and/or Board of Trustees. Our obligations under the Shares Registration Rights Agreement were fully satisfied in January 2018.