JBG SMITH Properties (JBGS) 10-Q 7 Nov 18 2018 Q3 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - USD ($)	9 Months Ended
	Sep. 30, 2018	Nov. 01, 2018	Jun. 30, 2017
Document And Entity Information [Abstract]
Entity Registrant Name	JBG SMITH PROPERTIES
Entity Central Index Key	1,689,796
Current Fiscal Year End Date	--12-31
Entity Filer Category	Non-accelerated Filer
Document Type	10-Q
Document Period End Date	Sep. 30, 2018
Document Fiscal Year Focus	2,018
Document Fiscal Period Focus	Q3
Amendment Flag	false
Entity Common Stock, Shares Outstanding		120,917,269
Entity Current Reporting Status	Yes
Entity Public Float			$ 0
Entity Emerging Growth Company	false
Entity Small Business	false

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Real estate, at cost:
Land and improvements	$ 1,366,154	$ 1,368,294
Buildings and improvements	3,678,335	3,670,268
Construction in progress, including land	649,056	978,942
Real estate, at cost	5,693,545	6,017,504
Less accumulated depreciation	(1,020,596)	(1,011,330)
Real estate, net	4,672,949	5,006,174
Cash and cash equivalents	253,148	316,676
Restricted cash	127,061	21,881
Tenant and other receivables, net	40,409	46,734
Deferred rent receivable, net	137,200	146,315
Investments in and advances to unconsolidated real estate ventures	361,014	261,811
Other assets, net	281,958	263,923
Assets Held-for-sale, Not Part of Disposal Group	137,455	8,293
TOTAL ASSETS	6,011,194	6,071,807
Liabilities:
Mortgages payable, net	1,769,938	2,025,692
Revolving credit facility	0	115,751
Unsecured term loans, net	296,981	46,537
Accounts payable and accrued expenses	147,211	138,607
Other liabilities, net	119,552	161,277
Liabilities held for sale	45,657	0
Total liabilities	2,379,339	2,487,864
Commitments and Contingencies
Redeemable noncontrolling interests	562,318	609,129
Shareholders' equity:
Preferred shares, $0.01 par value - 200,000 shares authorized, none issued	0	0
Common shares, $0.01 par value - 500,000 shares authorized; 120,917 and 117,955 shares issued and outstanding as of September 30, 2018 and December 31, 2017	1,210	1,180
Additional paid-in capital	3,150,899	3,063,625
Accumulated deficit	(110,219)	(95,809)
Accumulated other comprehensive income	24,132	1,612
Shareholders' equity / Former parent equity	3,066,022	2,970,608
Noncontrolling interests in consolidated subsidiaries	3,515	4,206
Total equity	3,069,537	2,974,814
TOTAL LIABILITIES, REDEEMABLE NONCONTROLLING INTERESTS AND EQUITY	$ 6,011,194	$ 6,071,807

Consolidated and Combined Balan

Consolidated and Combined Balance Sheets (Parenthetical) - $ / shares	Sep. 30, 2018	Dec. 31, 2017
Statement of Financial Position [Abstract]
Preferred shares, par value (in dollars per share)	$ 0.01	$ 0.01
Preferred shares, shares authorized	200,000,000	200,000,000
Preferred shares, shares issued	0	0
Preferred shares, shares outstanding	0	0
Common shares, par value (in dollars per share)	$ 0.01	$ 0.01
Common shares, shares authorized	500,000,000	500,000,000
Common shares, shares issued	120,917,000	117,955,000
Common shares, shares outstanding	120,917,000	117,955,000

Consolidated and Combined State

Consolidated and Combined Statements of Operations - USD ($) shares in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
REVENUE
Property rentals	$ 123,203,000	$ 116,458,000	$ 375,094,000	$ 316,899,000
Reimbursements from Tenants	9,744,000	9,593,000	28,651,000	27,161,000
Third-party real estate services, including reimbursements	23,788,000	25,141,000	72,278,000	38,881,000
Other income	1,708,000	1,158,000	4,904,000	3,701,000
Total revenue	158,443,000	152,350,000	480,927,000	386,642,000
EXPENSES
Depreciation and amortization	46,603,000	43,951,000	143,880,000	109,726,000
Property operating	34,167,000	29,634,000	95,462,000	77,341,000
Real estate taxes	16,905,000	17,194,000	54,024,000	47,978,000
General and administrative:
Corporate and other	12,415,000	10,593,000	37,759,000	35,536,000
Third-party real estate services	20,754,000	21,178,000	64,552,000	30,362,000
Share-based compensation related to Formation Transaction	8,387,000	14,445,000	26,912,000	14,445,000
Transaction and other costs	4,126,000	104,095,000	12,134,000	115,173,000
Operating Expenses	143,357,000	241,090,000	434,723,000	430,561,000
OPERATING INCOME (LOSS)	15,086,000	(88,740,000)	46,204,000	(43,919,000)
Income (loss) from unconsolidated real estate ventures, net	13,484,000	(1,679,000)	15,418,000	(1,365,000)
Interest and other income (loss), net	4,091,000	(379,000)	5,177,000	1,366,000
Interest expense	(18,979,000)	(15,309,000)	(56,263,000)	(43,813,000)
Gains (Losses) on Sales of Investment Real Estate	11,938,000	0	45,789,000	0
Loss on extinguishment of debt	(79,000)	(689,000)	(4,536,000)	(689,000)
Business Combination, Provisional Information, Initial Accounting Incomplete, Adjustment, Bargain Purchase, Reduction Of Gain	0	27,771,000	(7,606,000)	27,771,000
INCOME (LOSS) BEFORE INCOME TAX BENEFIT	25,541,000	(79,025,000)	44,183,000	(60,649,000)
Income tax benefit	841,000	1,034,000	1,436,000	317,000
NET INCOME (LOSS)	26,382,000	(77,991,000)	45,619,000	(60,332,000)
Net (income) loss attributable to redeemable noncontrolling interests	(3,552,000)	8,160,000	(6,532,000)	2,481,000
Net loss attributable to noncontrolling interests	0	0	(127,000)	0
NET INCOME (LOSS) ATTRIBUTABLE TO COMMON SHAREHOLDERS	$ 22,830,000	$ (69,831,000)	$ 39,214,000	$ (57,851,000)
EARNINGS (LOSS) PER COMMON SHARE:
Basic (in dollars per share)	$ 0.19	$ (0.61)	$ 0.33	$ (0.55)
Diluted (in dollars per share)	$ 0.19	$ (0.61)	$ 0.33	$ (0.55)
WEIGHTED AVERAGE NUMBER OF COMMON SHARES OUTSTANDING - basic and diluted (in shares)	119,835	114,744	118,588	105,347
Weighted Average Number of Shares Outstanding, Diluted	119,835	114,744	118,588	105,347

Consolidated and Combined Sta_2

Consolidated and Combined Statements of Comprehensive Income (Loss) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Statement of Comprehensive Income [Abstract]
NET INCOME (LOSS)	$ 26,382	$ (77,991)	$ 45,619	$ (60,332)
Other Comprehensive Income (Loss), Net of Tax [Abstract]
Change in fair value of derivative financial instruments	5,142	0	24,453	0
Reclassification of net loss on derivative financial instruments from accumulated other comprehensive income into interest expense	24	0	1,473	0
Other comprehensive income	(5,166)	0	(25,926)	0
COMPREHENSIVE INCOME (LOSS)	31,548	(77,991)	71,545	(60,332)
Net (income) loss attributable to redeemable noncontrolling interests	3,552	(8,160)	6,532	(2,481)
Other comprehensive income attributable to redeemable noncontrolling interests	(696)	0	(3,406)	0
Net loss attributable to noncontrolling interests	0	0	127	0
COMPREHENSIVE INCOME (LOSS) ATTRIBUTABLE TO JBG SMITH PROPERTIES	$ 27,300	$ (69,831)	$ 61,734	$ (57,851)

Consolidated and Combined Sta_3

Consolidated and Combined Statements of Equity - USD ($) shares in Thousands, $ in Thousands	Total	Common Shares	Additional Paid-In Capital	Accumulated Deficit	Accumulated Other Comprehensive Income	Former Parent Equity	Noncontrolling Interests in Consolidated Subsidiaries
Balance at beginning of period at Dec. 31, 2016	$ 2,121,984	$ 0	$ 0	$ 0	$ 0	$ 2,121,689	$ 295
Balance at beginning of period (in shares) at Dec. 31, 2016		0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net loss attributable to common shareholders	(57,851)			(28,827)			0
Net income (loss)	(60,332)
Deferred compensation shares and options, net	1,526					1,526
Contributions from former parent, net	334,843					334,843	0
Stock Repurchased During Period, Value	(96,632)					(96,632)
Stock Issued During Period, Shares, New Issues		94,736
Stock Issued During Period, Value, New Issues	0	$ (947)	(2,331,455)			(2,332,402)
Stock Issued During Period, Shares, Acquisitions		23,221
Issuance of common shares in connection with the Combination	864,918	$ 233	864,685
Noncontrolling Interest, Increase from Business Combination	3,987						3,987
Distributions to noncontrolling interests	(14)						(14)
Noncontrolling Interest, Contributions	134						134
Redeemable noncontrolling interest redemption value adjustment and other comprehensive income allocation	(97,084)		(97,084)
Other comprehensive income	0
Balance at end of period (in shares) at Sep. 30, 2017		117,957
Balance at end of period at Sep. 30, 2017	$ 3,075,811	$ 1,180	3,099,056	(28,827)	0	0	4,402
Common Stock, Dividends, Per Share, Declared	$ 0.45
Balance at beginning of period at Dec. 31, 2017	$ 2,974,814	$ 1,180	3,063,625	(95,809)	1,612	0	4,206
Balance at beginning of period (in shares) at Dec. 31, 2017	117,955	117,955
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net loss attributable to common shareholders	$ 39,087			39,214			(127)
Dividends	(53,624)			(53,624)
Net income (loss)	45,619
Stock Issued During Period, Value, New Issues	(109,122)	$ (30)	(109,092)
Issuance of common shares in connection with the Combination	0
Distributions to noncontrolling interests	(814)						(814)
Redeemable noncontrolling interest redemption value adjustment and other comprehensive income allocation	(24,752)		(21,346)		(3,406)
Other comprehensive income	25,926				25,926
Stockholders' Equity, Other	$ 472		472
Balance at end of period (in shares) at Sep. 30, 2018	120,917	120,917
Balance at end of period at Sep. 30, 2018	$ 3,069,537	$ 1,210	$ 3,150,899	$ (110,219)	$ 24,132	$ 0	$ 3,515

Consolidated and Combined Sta_4

Consolidated and Combined Statements of Cash Flows - USD ($)	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017
Statement of Cash Flows [Abstract]
Temporary Equity, Redemptions of OP Units	$ 109,208,000	$ 0
OPERATING ACTIVITIES:
Net income (loss)	45,619,000	(60,332,000)
Adjustments to reconcile net income (loss) to net cash provided by operating activities:
Share-based compensation expense	39,690,000	17,164,000
Depreciation and amortization, including amortization of debt issuance costs	146,958,000	111,684,000
Deferred rent	(7,880,000)	(9,249,000)
(Income) loss from unconsolidated real estate ventures, net	(15,418,000)	1,365,000
Amortization of above- and below-market lease intangibles, net	(58,000)	(872,000)
Amortization of lease incentives	3,646,000	2,492,000
Return on capital from unconsolidated real estate ventures	6,820,000	1,149,000
Reduction of gain (gain) on bargain purchase	7,606,000	(27,771,000)
Loss on extinguishment of debt	4,536,000	689,000
Gain on sale of real estate	(45,789,000)	0
Unrealized gain on interest rate swaps and caps	(1,264,000)	(467,000)
Bad debt expense	2,591,000	1,808,000
Other non-cash items	1,499,000	3,974,000
Changes in operating assets and liabilities:
Tenant and other receivables	2,167,000	(3,617,000)
Other assets, net	(18,637,000)	(32,884,000)
Accounts payable and accrued expenses	(23,875,000)	19,077,000
Other liabilities, net	(11,550,000)	(817,000)
Net cash provided by operating activities	136,661,000	23,393,000
INVESTING ACTIVITIES:
Development costs, construction in progress and real estate additions	(260,396,000)	(115,922,000)
Cash and restricted cash received in connection with the Combination, net		97,402,000
Proceeds from Sale of Real Estate	346,149,000	0
Acquisition of interests in unconsolidated real estate ventures, net of cash acquired	(386,000)	0
Distributions of capital from unconsolidated real estate ventures	2,240,000	0
Distribution of capital from sale of interest in an unconsolidated real estate venture	24,602,000	0
Investments in and advances to unconsolidated real estate ventures	(22,663,000)	(1,441,000)
Proceeds from Collection of Notes Receivable	0	50,934,000
Other investments	(665,000)	(3,531,000)
Proceeds from repayment of receivable from former parent	0	75,000,000
Net cash provided by investing activities	88,881,000	102,442,000
FINANCING ACTIVITIES:
Contributions from former parent, net	0	160,203,000
Acquisition of interest in consolidated real estate venture	548,000	0
Repayment of borrowings from former parent	0	(115,630,000)
Proceeds from borrowings from former parent	0	4,000,000
Capital lease payments	(82,000)	(17,776,000)
Borrowings under mortgages payable	43,823,000	242,018,000
Borrowings under revolving credit facility	35,000,000	115,751,000
Borrowings under unsecured term loans	250,000,000	50,000,000
Repayments of mortgages payable	(267,285,000)	(192,681,000)
Repayments of revolving credit facility	(150,751,000)	0
Debt issuance costs	(372,000)	(18,686,000)
Dividends paid to common shareholders	(80,166,000)
Distributions to redeemable noncontrolling interests	13,320,000	0
Proceeds from Noncontrolling Interests	250,000	134,000
Distributions to noncontrolling interests	(439,000)	(14,000)
Net cash (used in) provided by financing activities	(183,890,000)	227,319,000
Net increase in cash and cash equivalents and restricted cash	41,652,000	353,154,000
Cash and cash equivalents and restricted cash as of the beginning of the period	338,557,000	32,263,000
Cash and cash equivalents and restricted cash as of the end of the period	380,209,000	385,417,000
CASH AND CASH EQUIVALENTS AND RESTRICTED CASH AS OF END OF THE PERIOD:
Cash and cash equivalents and restricted cash	338,557,000	32,263,000
SUPPLEMENTAL DISCLOSURE OF CASH FLOW AND NON-CASH INFORMATION:
Cash paid for interest (net of capitalized interest of $14,863 and $2,285 in 2018 and 2017)	48,835,000	45,354,000
Accrued capital expenditures included in accounts payable and accrued expenses	78,910,000	17,633,000
Write-off of fully depreciated assets	23,049,000	24,909,000
Cash receipts from (payments for) income taxes	(114,000)	(3,681,000)
Issuance of common limited partnership units at the Separation	0	96,632,000
Issuance of common shares at the Separation	0	2,332,402,000
Issuance of common shares in connection with the Combination	0	864,918,000
Issuance of common limited partnership units in connection with the Combination	0	359,967,000
Contribution from former parent in connection with the Separation	$ 0	$ 174,639,000

Consolidated and Combined Sta_5

Consolidated and Combined Statements of Cash Flows (Parenthetical) $ in Thousands	9 Months Ended
	Sep. 30, 2018USD ($)
Statement of Cash Flows [Abstract]
Capitalized interest	$ 14,863
Interest Costs Capitalized

Organization and Basis of Prese

Organization and Basis of Presentation	9 Months Ended
	Sep. 30, 2018
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Organization and Basis of Presentation	Organization and Basis of Presentation Organization JBG SMITH Properties ("JBG SMITH") was organized by Vornado Realty Trust ("Vornado" or "former parent") as a Maryland real estate investment trust ("REIT") on October 27, 2016 (capitalized on November 22, 2016). JBG SMITH was formed for the purpose of receiving, via the spin-off on July 17, 2017 (the "Separation"), substantially all of the assets and liabilities of Vornado’s Washington, D.C. segment, which operated as Vornado / Charles E. Smith, (the "Vornado Included Assets"). On July 18, 2017, JBG SMITH acquired the management business and certain assets and liabilities (the "JBG Assets") of The JBG Companies ("JBG") (the "Combination"). The Separation and the Combination are collectively referred to as the "Formation Transaction." Unless the context otherwise requires, all references to "we," "us," and "our," refer to the Vornado Included Assets (our predecessor and accounting acquirer) for periods prior to the Separation and to JBG SMITH for periods after the Separation. References to "our share" refers to our ownership percentage of consolidated and unconsolidated assets in real estate ventures. Substantially all of our assets are held by, and our operations are conducted through, JBG SMITH Properties LP ("JBG SMITH LP"), our operating partnership. As of September 30, 2018 , we, as its sole general partner, controlled JBG SMITH LP and owned 87.8% of its common limited partnership units ("OP Units"). Prior to the Separation from Vornado, JBG SMITH was a wholly owned subsidiary of Vornado and had no material assets or operations. Our operations are presented as if the transfer of the Vornado Included Assets had been consummated prior to all historical periods presented in the accompanying consolidated and combined financial statements at the carrying amounts of such assets and liabilities reflected in Vornado’s books and records. The assets and liabilities of the JBG Assets and subsequent results of operations and cash flows are reflected in our consolidated and combined financial statements beginning on the date of the Combination. We own and operate a portfolio of high-quality office and multifamily assets, many of which are amenitized with ancillary retail. Our portfolio reflects our longstanding strategy of owning and operating assets within Metro-served submarkets in the Washington, D.C. metropolitan area that have high barriers to entry and key urban amenities, including being within walking distance of a Metro station. As of September 30, 2018 , our Operating Portfolio consists of 65 operating assets comprising 46 office assets totaling approximately 13.0 million square feet ( 11.5 million square feet at our share), 15 multifamily assets totaling 6,307 units ( 4,523 units at our share) and four other assets totaling approximately 806,000 square feet ( 352,000 square feet at our share). Additionally, we have (i) seven assets under construction comprising three office assets totaling approximately 778,000 square feet ( 546,000 square feet at our share) and four multifamily assets totaling 1,476 units ( 1,284 units at our share); and (ii) 43 future development assets totaling approximately 22.4 million square feet ( 19.0 million square feet at our share) of estimated potential development density. Our revenues are derived primarily from leases with office and multifamily tenants, including fixed rents and reimbursements from tenants for certain expenses such as real estate taxes, property operating expenses, and repairs and maintenance. In addition, we have a third-party real estate services business that provides fee-based real estate services to the legacy funds (the "JBG Legacy Funds") formerly organized by JBG and other third parties. Basis of Presentation The accompanying unaudited condensed consolidated and combined financial statements and notes are prepared in accordance with accounting principles generally accepted in the United States of America ("GAAP") for interim financial information and with the instructions of Form 10-Q and Article 10 of Regulation S-X. Accordingly, these unaudited condensed consolidated and combined financial statements do not contain certain information required in annual financial statements and notes as required under GAAP. In our opinion, all adjustments considered necessary for a fair presentation have been included, and all such adjustments are of a normal recurring nature. All intercompany transactions and balances have been eliminated. The results of operations for the three and nine months ended September 30, 2018 and 2017 are not necessarily indicative of the results that may be expected for a full year. These condensed consolidated and combined financial statements should be read in conjunction with our Annual Report on Form 10-K for the year ended December 31, 2017 , filed with the Securities and Exchange Commission. The accompanying condensed consolidated and combined financial statements include the accounts of JBG SMITH and our wholly owned subsidiaries and those other entities, including JBG SMITH LP, in which we have a controlling financial interest, including where we have been determined to be the primary beneficiary of a variable interest entity ("VIE"). See Note 5 for additional information on our VIEs. The portions of the equity and net income of consolidated subsidiaries that are not attributable to JBG SMITH are presented separately as amounts attributable to noncontrolling interests in our condensed consolidated and combined financial statements. References to the financial statements refer to our condensed consolidated and combined financial statements as of September 30, 2018 and December 31, 2017 , and for the three and nine months ended September 30, 2018 and 2017 . References to the balance sheets refer to our condensed consolidated balance sheets as of September 30, 2018 and December 31, 2017 . References to the statements of operations refer to our condensed consolidated and combined statements of operations for the three and nine months ended September 30, 2018 and 2017 . References to the statements of cash flows refer to our condensed consolidated and combined statements of cash flows for the nine months ended September 30, 2018 and 2017 . Formation Transaction JBG SMITH and the Vornado Included Assets were under common control of Vornado for all periods prior to the Separation. The transfer of the Vornado Included Assets from Vornado to JBG SMITH was completed prior to the Separation, at net book values (historical carrying amounts) carved out from Vornado’s books and records. For purposes of the formation of JBG SMITH, the Vornado Included Assets were designated as the predecessor and the accounting acquirer of the JBG Assets. Consequently, the financial statements of JBG SMITH, as set forth herein, represent a continuation of the financial information of the Vornado Included Assets as the predecessor and accounting acquirer such that the historical financial information included herein as of any date or for any periods on or prior to the completion of the Combination represents the pre-Combination financial information of the Vornado Included Assets. The financial statements reflect the common shares as of the date of the Separation as outstanding for all periods prior to July 17, 2017. The acquisition of the JBG Assets completed subsequently by JBG SMITH was accounted for as a business combination using the acquisition method whereby identifiable assets acquired and liabilities assumed are recorded at acquisition-date fair values and income and cash flows from the operations were consolidated into the financial statements of JBG SMITH commencing July 18, 2017. Consequently, the financial statements for the periods before and after the Formation Transaction are not directly comparable. The accompanying financial statements as of September 30, 2018 and December 31, 2017 and for the three and nine months ended September 30, 2018 include our consolidated accounts. The results of operations for the three and nine months ended September 30, 2017 reflect the aggregate operations and changes in cash flows and equity on a combined basis for all periods prior to July 17, 2017 and on a consolidated basis for all periods subsequent to July 17, 2017. Therefore, our results of operations, cash flows and financial condition set forth in this report for the three and nine months ended September 30, 2017 are not necessarily indicative of our future results of operations, cash flows or financial condition as an independent, publicly traded company. The historical financial results for the Vornado Included Assets reflect charges for certain corporate costs allocated by the former parent, which were based on either actual costs incurred or a proportion of costs estimated to be applicable, to the Vornado Included Assets based on an analysis of key metrics, including total revenues. Such costs do not necessarily reflect what the actual costs would have been if JBG SMITH had been operating as a separate standalone public company. See Note 16 for additional information. The following pro forma information for the three and nine months ended September 30, 2017 is presented as if the Formation Transaction had occurred on January 1, 2016. This pro forma information is based upon historical financial statements, adjusted for certain factually supported items directly related to the Formation Transaction. This pro forma information does not purport to represent what the actual results of our operations would have been, nor does it purport to predict the results of operations of future periods. The pro forma information was adjusted to exclude transaction and other costs of $104.1 million and $115.2 million for the three and nine months ended September 30, 2017 . Three Months Ended Nine Months Ended September 30, 2017 (In thousands) Pro forma information: Total revenue $ 160,428 $ 481,314 Net income (loss) attributable to common shareholders 2,283 (13,741 ) The total revenue of the JBG Assets for the three and nine months ended September 30, 2017 included in our statements of operations from the acquisition date was $34.9 million . The net loss from the JBG Assets for the three and nine months ended September 30, 2017 included in our statements of operations from the acquisition date was $7.8 million . The Combination resulted in a gain on bargain purchase of $27.8 million for the three and nine months ended September 30, 2017 because the fair value of the identifiable net assets acquired exceeded the purchase consideration. During the fourth quarter of 2017, this gain was reduced by $3.4 million . As a result of finalizing our fair value estimates used in the purchase price allocation related to the Combination, during the three months ended June 30, 2018, we adjusted the fair value of certain assets acquired and liabilities assumed consisting of a decrease of $468,000 to investments in and advances to unconsolidated real estate ventures, an increase of $4.7 million to lease assumption liabilities and an increase of $2.4 million to other liabilities acquired, resulting in a reduction of the gain on bargain purchase of $7.6 million for the nine months ended September 30, 2018 . Income Taxes We have elected to be taxed as a REIT under sections 856-860 of the Internal Revenue Code of 1986, as amended (the "Code"). Under those sections, a REIT which distributes at least 90% of its REIT taxable income as dividends to its shareholders each year and which meets certain other conditions will not be taxed on that portion of its taxable income which is distributed to its shareholders. Prior to the Separation, Vornado operated as a REIT and distributed 100% of taxable income to its shareholders, accordingly, no provision for federal income taxes has been made in the accompanying financial statements for the periods prior to the Separation. We intend to adhere to these requirements and maintain our REIT status in future periods. We also participate in the activities conducted by subsidiary entities which have elected to be treated as taxable REIT subsidiaries under the Code. As such, we are subject to federal, state, and local taxes on the income from these activities.

Summary of Significant Accounti

Summary of Significant Accounting Policies	9 Months Ended
	Sep. 30, 2018
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	Summary of Significant Accounting Policies Significant Accounting Policies There were no material changes to our significant accounting policies disclosed in our Annual Report on Form 10-K for the year ended December 31, 2017 . Use of Estimates The preparation of the financial statements in conformity with GAAP requires us to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities as of the date of the financial statements and the reported amounts of revenue and expenses during the reporting period. The most significant of these estimates include: (i) the underlying cash flows used to establish the fair values recorded in connection with the Combination and used in assessing impairment and (ii) the determination of useful lives for tangible and intangible assets. Actual results could differ from these estimates. Recent Accounting Pronouncements In connection with the adoption of Accounting Standards Update ("ASU") ASU 2016-18, Statement of Cash Flows (Topic 230): Restricted Cash, we revised the presentation of restricted cash in the statement of cash flows for the nine months ended September 30, 2017 . The following table provides a brief description of recent accounting pronouncements by the Financial Accounting Standards Board ("FASB") that could have a material effect on our financial statements: Standard Description Date of Adoption Effect on the Financial Statements or Other Significant Matters Standard adopted ASU 2014-09, Revenue from Contracts with Customers (Topic 606), as clarified and amended by ASU 2016-08, ASU 2016-10 and ASU 2016-12 This standard establishes a single comprehensive model for entities to use in accounting for revenue arising from contracts with customers and supersedes most of the existing revenue recognition guidance. It requires an entity to recognize revenue when it transfers promised goods or services to customers in an amount that reflects the consideration to which the entity expects to be entitled in exchange for those goods or services and also requires certain additional disclosures. January 2018 We utilized the modified retrospective method of adoption. The standard excludes from its scope the areas of accounting that most significantly affect our revenue recognition, including accounting for leases and financial instruments. Our evaluation determined there were no required changes to our recognition of revenue related to our third-party real estate services, tenant reimbursements, property and asset management fees, or transactional/management fees for leasing, development and construction. Our evaluation also determined there were no required changes to our recognition of promote fees and dispositions of real estate properties as we did not have any deferred gains due to continuing involvement at the time of adoption. Therefore, the adoption of this standard did not have a material impact on our financial statements. We adopted the practical expedient of this standard to only assess the recognition of revenue for open contracts at the date of adoption and there was no adjustment to the opening balance of our accumulated deficit at January 1, 2018. The comparative information has not been restated and continues to be reported under the accounting standards in effect for that period. Standard Description Date of Adoption Effect on the Financial Statements or Other Significant Matters Standards not yet adopted ASU 2016-02, Leases (Topic 842), as clarified and amended by ASU 2018-01, ASU 2018-10 and ASU 2018-11 This standard establishes principles for the recognition, measurement, presentation and disclosure of leases for both lessees and lessors. ASU 2016-02 requires lessees to apply a dual approach, classifying leases as either finance or operating leases based on the principle of whether or not the lease is effectively a financed purchase. Lessees are required to record a right-of-use asset and a lease liability for all leases with a term of greater than 12 months. Leases with a term of 12 months or less will be accounted for similar to existing guidance for operating leases. Lessees will recognize expense based on the effective interest method for finance leases or on a straight-line basis for operating leases. The ASU also clarifies that an assessment of whether a land easement meets the definition of a lease under the new lease standard is required. The provisions of this standard are effective for fiscal years beginning after December 15, 2018 and should be applied through a modified retrospective transition, which includes optional practical expedients related to leases that commenced before the effective date and allows the new requirements to be applied on the date of adoption rather than the beginning of the earliest comparative period presented. January 2019 We are currently evaluating the overall impact of the adoption of ASU 2016-02 on our financial statements. ASU 2016-02 will more significantly impact the accounting for leases in which we are the lessee. We have ground leases for which we will be required to record a right-of-use asset and lease liability equal to the present value of the remaining minimum lease payments upon adoption of this standard. As of September 30, 2018, future ground lease payments totaled $573.9 million to which we would apply a discount rate. We are in the process of determining an appropriate discount rate. Under ASU 2016-02, initial direct costs for both lessees and lessors would include only those costs that are incremental to the arrangement and would not have been incurred if the lease had not been obtained. As a result, we will no longer be able to capitalize internal leasing costs and instead will be required to expense these costs as incurred. Capitalized internal leasing costs were $1.5 million and $1.0 million for the three months ended September 30, 2018 and 2017, and $4.3 million and $1.8 million for the nine months ended September 30, 2018 and 2017. We will apply the modified retrospective approach of adoption and anticipate electing the package of practical expedients that allows an entity to not reassess (i) whether any expired or existing contracts are or contain leases, (ii) lease classifications for any expired or existing leases and (iii) initial direct costs for any expired or existing leases. ASU 2018-09, Codification Improvements These amendments provide clarifications and corrections to certain ASC subtopics including the following: 220-10 (Income Statement - Reporting Comprehensive Income - Overall), 470-50 (Debt - Modifications and Extinguishments), 480-10 (Distinguishing Liabilities from Equity - Overall), 718-740 (Compensation - Stock Compensation - Income Taxes), 805-740 (Business Combinations - Income Taxes), 815-10 (Derivatives and Hedging - Overall), and 820-10 (Fair Value Measurement - Overall). January 2019 The updates related to Subtopics 470-50 and 820-10 were effective immediately and their adoption did not have an impact on our financial statements. We are currently evaluating the remaining guidance to determine the impact it may have on our financial statements.

Disposals and Assets Held for S

Disposals and Assets Held for Sale (Notes)	9 Months Ended
	Sep. 30, 2018
Discontinued Operations and Disposal Groups [Abstract]
Mergers, Acquisitions and Dispositions Disclosures [Text Block]	Dispositions and Assets Held for Sale Dispositions The following is a summary of disposition activity for the nine months ended September 30, 2018 : Date Disposed Assets Segment Location Total Square Feet Gross Sales Price Cash Proceeds from Sale (1) Gain on Sale (In thousands) February 13, 2018 Summit - MWAA Other Reston, Virginia — $ 2,154 $ 2,154 $ 455 April 3, 2018 Summit I and II / Summit Land (2) Office Reston, Virginia 284,118 95,000 35,240 6,189 May 1, 2018 Bowen Building (3) Office Washington, D.C. 231,402 140,000 136,488 27,207 September 21, 2018 Executive Tower (4) Office Washington, D.C. 129,831 121,445 113,267 11,938 Total 645,351 $ 358,599 $ 287,149 $ 45,789 ______________ (1) Net of related mortgage loan payments. (2) Total square feet included 700,000 square feet of estimated potential development density. In connection with the sale, we repaid the related $59.0 million mortgage loan. (3) In connection with the sale, we repaid $115.0 million of the then outstanding balance on our revolving credit facility. (4) Proceeds from the sale were held in escrow and classified as "Restricted cash" on our balance sheet as of September 30, 2018 . In August 2018, JP Morgan, our partner in the real estate venture that owned the Investment Building, a 401,000 square foot office building located in Washington, D.C., acquired our 5.0% interest in the venture. See Note 4 for additional information. Assets Held for Sale We have certain real estate properties that are expected to be sold to third parties within a one-year period that meet the criteria to be classified as held for sale as of September 30, 2018 . The amounts included in "Assets held for sale" in our balance sheets primarily represent real estate investment balances. The amounts included in "Liabilities related to assets held for sale" in our balance sheets primarily represent mortgage payable balances for these properties. The following is a summary of assets held for sale as of September 30, 2018 : Assets Segment Location Total Square Feet Assets Held for Sale Liabilities Related to Assets Held for Sale (In thousands) 1233 20th Street (1) Office Washington, D.C. 149,684 $ 59,602 $ 43,802 Falkland Chase-North (2) Multifamily Downtown Silver Spring, Maryland 13,284 2,218 — Commerce Executive (3) Office / Other Reston, Virginia 388,450 75,635 1,855 551,418 $ 137,455 $ 45,657 _______________ (1) Liabilities related to assets held for sale includes a mortgage loan of $42.0 million as of September 30, 2018 . In October 2018, we sold 1233 20th Street for a gross sales price of $65.0 million . In connection with the sale, we repaid the related mortgage loan. (2) In October 2018, we sold the out-of-service portion of Falkland Chase-North for a gross sales price of $3.8 million . (3) In July 2018, the buyer’s deposit related to the contract to sell Commerce Executive for $115.0 million became non-refundable. The sale is expected to close in early 2019.

Investments in and Advances to

Investments in and Advances to Unconsolidated Real Estate Ventures	9 Months Ended
	Sep. 30, 2018
Equity Method Investments and Joint Ventures [Abstract]
Investments in and Advances to Unconsolidated Real Estate Ventures	Investments in and Advances to Unconsolidated Real Estate Ventures The following is a summary of the composition of our investments in and advances to unconsolidated real estate ventures: Real Estate Venture Partners Ownership Interest (1) September 30, 2018 December 31, 2017 (In thousands) Canadian Pension Plan Investment Board ("CPPIB") 55.0% - 79.2% $ 136,877 $ 36,317 Landmark 1.8% - 49.0% 86,561 95,368 CBREI Venture 5.0% - 64.0% 75,713 79,062 Berkshire Group 50.0% 38,124 27,761 Brandywine 30.0% 13,858 13,741 CIM Group ("CIM") and Pacific Life Insurance Company ("PacLife") 16.7% 9,664 — JP Morgan —% — 9,296 Other 137 246 Total investments in unconsolidated real estate ventures 360,934 261,791 Advances to unconsolidated real estate ventures 80 20 Total investments in and advances to unconsolidated real estate ventures $ 361,014 $ 261,811 _______________ (1) Ownership interests as of September 30, 2018 . We have multiple investments with certain venture partners with varying ownership interests. In January 2018, we invested $10.1 million for a 16.67% interest in a real estate venture with CIM and PacLife, which purchased the 1,152-key Wardman Park hotel, located adjacent to the Woodley Park Metro Station in northwest Washington, D.C. Prior to the acquisition by this venture, the JBG Legacy Funds owned a 47.64% interest in the Wardman Park hotel. The JBG Legacy Funds did not receive any proceeds from the sale, as the net proceeds were used to satisfy the prior mortgage debt. A third-party asset manager oversees the hotel operations on behalf of the venture and our involvement will increase only to the extent the land development opportunity becomes the primary business plan for the asset. In February 2018, we entered into a real estate venture with CPPIB to develop and own 1900 N Street, an under construction office asset in Washington, D.C. We contributed 1900 N Street, valued at $95.9 million , to the real estate venture, and CPPIB has committed to contribute approximately $101.0 million to the venture for a 45.0% interest, which will reduce our ownership interest from 100.0% at the real estate venture's formation to 55.0% as contributions are funded. In June 2018, the real estate venture with CPPIB that owns 1101 17th Street, a 216,000 square foot office building located in Washington, D.C., in which we have a 55.0% ownership interest, refinanced a mortgage loan payable that was collateralized by the property. The terms of the new mortgage loan eliminated the principal guaranty provisions that had been included in the prior loan. Distributions and our share of the cumulative earnings of the venture exceeded our investment in the venture by $5.4 million , which resulted in a negative investment balance. After the elimination of the principal guaranty provisions in the prior mortgage loan, we no longer guarantee the obligations of the venture or provide further financial support to the venture. Accordingly, we recognized the $5.4 million negative investment balance as income within “Income from unconsolidated real estate ventures, net” in our statements of operations for the nine months ended September 30, 2018 . We have also suspended the equity method accounting for this real estate venture. We will recognize as income any future distributions from the venture until our share of unrecorded earnings and contributions exceed the cumulative excess distributions previously recognized in income. For the three and nine months ended September 30, 2018 , we recognized income of $890,000 related to a distribution from 1101 17th Street, which is included in “Income from unconsolidated real estate ventures, net” in our statement of operations. In August 2018, JP Morgan, our partner in the real estate venture that owned the Investment Building, a 401,000 square foot office building located in Washington, D.C., acquired our 5.0% interest in the venture for $24.6 million , resulting in a gain of $15.5 million , which is included in "Income from unconsolidated real estate ventures, net” in our statements of operations for the three and nine months ended September 30, 2018 . The following is a summary of the debt of our unconsolidated real estate ventures: Weighted Average Effective (1) September 30, 2018 December 31, 2017 (In thousands) Variable rate (2) 4.96% $ 536,950 $ 534,500 Fixed rate (3) 3.95% 852,674 657,701 Unconsolidated real estate ventures - mortgages payable 1,389,624 1,192,201 Unamortized deferred financing costs (2,555 ) (2,000 ) Unconsolidated real estate ventures - mortgages payable, net (4) $ 1,387,069 $ 1,190,201 ______________ (1) Weighted average effective interest rate as of September 30, 2018 . (2) Includes variable rate mortgages payable with interest rate cap agreements. (3) Includes variable rate mortgages payable with interest rates fixed by interest rate swap agreements. (4) See Note 15 for additional information on guarantees of the debt of certain of our unconsolidated real estate ventures. The following is a summary of the financial information for our unconsolidated real estate ventures: September 30, 2018 December 31, 2017 Combined balance sheet information: (In thousands) Real estate, net $ 2,425,633 $ 2,106,670 Other assets, net 307,105 264,731 Total assets $ 2,732,738 $ 2,371,401 Mortgages payable, net $ 1,387,069 $ 1,190,201 Other liabilities, net 100,104 76,416 Total liabilities 1,487,173 1,266,617 Total equity 1,245,565 1,104,784 Total liabilities and equity $ 2,732,738 $ 2,371,401 Three Months Ended September 30, Nine Months Ended September 30, 2018 2017 2018 2017 Combined income statement information: (In thousands) Total revenue $ 76,247 $ 46,830 $ 236,938 $ 83,387 Operating income 6,861 3,237 23,719 14,576 Net loss (6,970 ) (5,191 ) (12,159 ) (414 )

Variable Interest Entities

Variable Interest Entities	9 Months Ended
	Sep. 30, 2018
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Variable Interest Entities	Variable Interest Entities We hold various interests in entities deemed to be VIEs, which we evaluate at acquisition, formation, after a change in the ownership agreement or a change in the real estate venture's economics to determine if the VIEs should be consolidated in our financial statements or should no longer be considered a VIE. Certain criteria we assess in determining whether the VIEs should be consolidated relate to our at-risk equity, our control over significant business activities, our voting rights, the noncontrolling interest kick-out rights and whether we are the primary beneficiary of the VIE. Unconsolidated VIEs As of September 30, 2018 and December 31, 2017 , we have interests in entities deemed to be VIEs that are in the development stage and do not hold sufficient equity at risk or conduct substantially all their operations on behalf of an investor with disproportionately few voting rights. Although we are engaged to act as the managing partner in charge of day-to-day operations of these investees, we are not the primary beneficiary of these VIEs as we do not hold unilateral power over activities that, when taken together, most significantly impact the respective VIE’s performance. We account for our investment in these entities under the equity method. As of September 30, 2018 and December 31, 2017 , the net carrying amounts of our investment in these entities were $269.1 million and $163.5 million , which are included in "Investments in and advances to unconsolidated real estate ventures" in our balance sheets. Our equity in the income of unconsolidated VIEs is included in "Income from unconsolidated real estate ventures, net" in our statements of operations. Our maximum exposure to loss in these entities is limited to our investments, construction commitments and debt guarantees. See Note 15 for additional information. Consolidated VIEs JBG SMITH LP is our most significant consolidated VIE. We hold the majority membership interest in the operating partnership, act as the general partner and exercise full responsibility, discretion and control over its day-to-day management. The noncontrolling interests of the operating partnership do not have substantive liquidation rights, substantive kick-out rights without cause, or substantive participating rights that could be exercised by a simple majority of noncontrolling interest members (including by such a member unilaterally). Because the noncontrolling interest holders do not have these rights, the operating partnership is a VIE. As general partner, we have the power to direct the core activities of the operating partnership that most significantly affect its performance, and through our majority interest in the operating partnership have both the right to receive benefits from and the obligation to absorb losses of the operating partnership. Accordingly, we are the primary beneficiary of the operating partnership and consolidate the operating partnership in our financial statements. As we conduct our business and hold our assets and liabilities through the operating partnership, the total assets and liabilities of the operating partnership comprise substantially all of our consolidated assets and liabilities. We also consolidate certain VIEs in which we control the most significant business activities. These entities are VIEs because they are in the development stage and do not hold sufficient equity at risk. We are the primary beneficiaries of these VIEs because the noncontrolling interest holders do not have substantive kick-out or participating rights and we control all of the significant business activities. As of September 30, 2018 , we consolidated two VIEs with total assets and liabilities, excluding the operating partnership, of $188.4 million and $22.8 million . As of December 31, 2017 , we consolidated two VIEs with total assets and liabilities, excluding the operating partnership, of $111.0 million and $8.8 million .

Other Assets, Net

Other Assets, Net	9 Months Ended
	Sep. 30, 2018
Deferred Costs, Capitalized, Prepaid, and Other Assets Disclosure [Abstract]
Other Assets, Net	Other Assets, Net The following is a summary of other assets, net: September 30, 2018 December 31, 2017 (In thousands) Deferred leasing costs $ 189,959 $ 171,153 Accumulated amortization (72,217 ) (67,180 ) Deferred leasing costs, net 117,742 103,973 Prepaid expenses 14,623 9,038 Identified intangible assets, net 94,221 126,467 Deferred financing costs on credit facility, net 5,292 6,654 Deposits 3,592 6,317 Derivative agreements, at fair value 28,356 2,141 Other 18,132 9,333 Total other assets, net $ 281,958 $ 263,923

Debt

Debt	9 Months Ended
	Sep. 30, 2018
Debt Disclosure [Abstract]
Debt	Debt Mortgages Payable The following is a summary of mortgages payable: Weighted Average (1) September 30, 2018 December 31, 2017 (In thousands) Variable rate (2) 4.16% $ 182,996 $ 498,253 Fixed rate (3) (4) 4.19% 1,590,983 1,537,706 Mortgages payable 1,773,979 2,035,959 Unamortized deferred financing costs and premium/ discount, net (4,041 ) (10,267 ) Mortgages payable, net $ 1,769,938 $ 2,025,692 __________________________ (1) Weighted average effective interest rate as of September 30, 2018 . (2) Includes variable rate mortgages payable with interest rate cap agreements. (3) Includes variable rate mortgages payable with interest rates fixed by interest rate swap agreements. (4) Excludes the mortgage payable of $42.0 million related to 1233 20th Street, which is included in "Liabilities related to assets held for sale" in our balance sheet as of September 30, 2018 . This mortgage was repaid in October 2018 concurrent with the closing of the sale. See Note 3 for additional information. As of September 30, 2018 , the net carrying value of real estate collateralizing our mortgages payable, excluding assets held for sale, totaled $2.3 billion . Our mortgage loans contain covenants that limit our ability to incur additional indebtedness on these properties and in certain circumstances, require lender approval of tenant leases and/or yield maintenance upon repayment prior to maturity. Certain of our mortgage loans are recourse to us. During the nine months ended September 30, 2018 , aggregate borrowings related to construction draws under mortgages payable totaled $43.8 million . We repaid mortgages payable with an aggregate principal balance of $251.1 million and recognized losses on the extinguishment of debt in conjunction with these repayments of $79,000 and $4.5 million for the three and nine months ended September 30, 2018 . As of September 30, 2018 and December 31, 2017 , we had various interest rate swap and cap agreements with an aggregate notional value of $1.3 billion and $1.4 billion on certain of our mortgages payable, which mature on various dates concurrent with the maturity of the related mortgages payable. During the nine months ended September 30, 2018 , we entered into various interest rate swap and cap agreements on certain of our mortgages payable with an aggregate notional value of $381.3 million . See Note 13 for additional information. Credit Facility Our $1.4 billion credit facility, consists of a $1.0 billion revolving credit facility maturing in July 2021 , with two six -month extension options, a delayed draw $200.0 million unsecured term loan ("Tranche A-1 Term Loan") maturing in January 2023 , and a delayed draw $200.0 million unsecured term loan ("Tranche A-2 Term Loan") maturing in July 2024 . In January 2018, we drew $50.0 million under the Tranche A-1 Term Loan in accordance with the delayed draw provisions of the credit facility, bringing the outstanding borrowings under the term loan facility to $100.0 million . Concurrent with the draw, we entered into an interest rate swap agreement to convert the variable interest rate to a fixed interest rate. As of September 30, 2018 and December 31, 2017 , we had interest rate swaps with an aggregate notional value of $100.0 million and $50.0 million to convert the variable interest rate applicable to our Tranche A-1 Term Loan to a fixed interest rate, providing weighted average base interest rates under the facility agreement of 2.12% and 1.97% per annum. The interest rate swaps mature in January 2023, concurrent with the maturity of our Tranche A-1 Term Loan. In July 2018, we drew $200.0 million under the Tranche A-2 Term Loan, in accordance with the delayed draw provisions of the credit facility. The following is a summary of amounts outstanding under the credit facility: Interest Rate (1) September 30, 2018 December 31, 2017 (In thousands) Revolving credit facility (2) (3) (4) (5) 3.36% $ — $ 115,751 Tranche A-1 Term Loan 3.32% $ 100,000 $ 50,000 Tranche A-2 Term Loan 3.81% 200,000 — Unsecured term loans 300,000 50,000 Unamortized deferred financing costs, net (3,019 ) (3,463 ) Unsecured term loans, net $ 296,981 $ 46,537 __________________________ (1) Interest rate as of September 30, 2018 . (2) As of September 30, 2018 and December 31, 2017 , letters of credit with an aggregate face amount of $5.7 million were provided under our revolving credit facility. (3) As of September 30, 2018 and December 31, 2017 , net deferred financing costs related to our revolving credit facility totaling $5.3 million and $6.7 million were included in "Other assets, net." (4) In May 2018, in connection with the sale of the Bowen Building, we repaid $115.0 million of the then outstanding balance on our revolving credit facility. See Note 3 for additional information. (5) The interest rate for the revolving credit facility excludes a 0.15% facility fee.

Other Liabilities, Net

Other Liabilities, Net	9 Months Ended
	Sep. 30, 2018
Other Liabilities Disclosure [Abstract]
Other Liabilities, Net	Other Liabilities, Net The following is a summary of other liabilities, net: September 30, 2018 December 31, 2017 (In thousands) Lease intangible liabilities $ 40,179 $ 44,917 Accumulated amortization (25,523 ) (26,950 ) Lease intangible liabilities, net 14,656 17,967 Prepaid rent 15,030 15,751 Lease assumption liabilities and accrued tenant incentives 49,510 50,866 Capital lease obligation 15,736 15,819 Security deposits 13,009 13,618 Ground lease deferred rent payable 3,498 3,730 Net deferred tax liability 6,446 8,202 Dividends payable (1) — 31,097 Other 1,667 4,227 Total other liabilities, net $ 119,552 $ 161,277 ________________________________________ (1) Dividends declared in December 2017 were paid in January 2018.

Redeemable Noncontrolling Inter

Redeemable Noncontrolling Interests	9 Months Ended
	Sep. 30, 2018
Noncontrolling Interest [Abstract]
Redeemable Noncontrolling Interests	Redeemable Noncontrolling Interests JBG SMITH LP In July 2017, JBG SMITH LP issued 19.8 million OP Units to persons other than JBG SMITH that became redeemable for cash or, at our election, our common shares beginning on August 1, 2018, subject to certain limitations. During the three and nine months ended September 30, 2018 , unitholders redeemed 3.0 million OP units, which we elected to redeem for an equivalent number of our common shares. As of September 30, 2018 , outstanding OP Units totaled 16.8 million , representing a 12.2% interest in JBG SMITH LP. On our balance sheets, our redeemable noncontrolling interests are presented at the higher of their redemption value at the end of each reporting period or their carrying value, with such adjustments recognized in "Additional paid-in capital." Redemption value is equivalent to the market value of one of our common shares at the end of the period multiplied by the number of vested OP units outstanding. Consolidated Real Estate Venture In November 2017, we became a partner in a real estate venture that owns an under construction multifamily asset located at 965 Florida Avenue in Washington, D.C. Pursuant to the terms of the 965 Florida Avenue real estate venture agreement, we will fund all capital contributions until our ownership interest reaches a maximum of 97.0% . Our partner can redeem its interest for cash two years after delivery, but no later than seven years subsequent to delivery. As of September 30, 2018 , we held an 85.4% ownership interest. Below is a summary of the activity of redeemable noncontrolling interests: Nine Months Ended September 30, 2018 2017 JBG SMITH LP Consolidated Real Estate Venture Total JBG SMITH LP Consolidated Real Estate Venture Total (In thousands) Balance as of beginning of period $ 603,717 $ 5,412 $ 609,129 $ — $ — $ — Fair value of OP Unit redemptions (109,208 ) — (109,208 ) — — — OP Units issued at the Separation — — — 96,632 — 96,632 OP Units issued in connection with the Combination (1) — — — 359,967 — 359,967 Net income (loss) attributable to redeemable noncontrolling interests 6,537 (5 ) 6,532 (2,481 ) — (2,481 ) Other comprehensive income 3,406 — 3,406 — — — Contributions (distributions) (8,763 ) 500 (8,263 ) — — — Share-based compensation expense 39,376 — 39,376 15,799 — 15,799 Adjustment to redemption value 21,346 — 21,346 97,084 — 97,084 Balance as of end of period $ 556,411 $ 5,907 $ 562,318 $ 567,001 $ — $ 567,001 (1) Excludes certain OP Units issued as part of the Combination which had an estimated fair value of $110.6 million , the vesting of which is subject to post-combination employment.

Share-Based Payments and Employ

Share-Based Payments and Employee Benefits	9 Months Ended
	Sep. 30, 2018
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Share-Based Payments and Employee Benefits	Share-Based Payments Time-Based LTIP Units In February 2018, we granted 357,759 long-term incentive partnership units ("LTIP Units") with time-based vesting requirements ("Time-Based LTIP Units") to management and other employees with a grant-date fair value of $11.2 million or $31.38 per unit. The significant assumptions used to value the Time-Based LTIP Units included expected volatility ( 20.0% ), risk-free interest rate ( 2.1% ) and post-grant restriction periods ( 2 years ). The Time-Based LTIP units vest in four equal installments in January of each year, subject to continued employment. Compensation expense is being recognized over a four -year period. Performance-Based LTIP Units In February 2018, we granted 553,489 LTIP Units with performance-based vesting requirements ("Performance-Based LTIP Units") to management and other employees with a grant-date fair value of $9.4 million or $17.04 per unit valued using Monte Carlo simulations. The significant assumptions used to value the Performance-Based LTIP Units included expected volatility ( 19.9% ), dividend yield ( 2.7% ) and risk-free interest rates ( 2.3% ). Fifty percent of any Performance-Based LTIP Units that are earned vest at the end of the three -year performance period and the remaining 50% one year after the performance period ends, subject to continued employment. Compensation expense is being recognized over a four -year period. LTIP Units In May 2018, as part of their annual compensation, we granted a total of 25,770 fully vested LTIP Units to certain of our trustees with an aggregate grant-date fair value of $794,000 . Other Equity Awards Certain executives have elected to receive all or a portion of any cash bonus that may be paid in 2019, related to 2018 service, in the form of fully vested LTIP Units. Share-Based Compensation Expense Share-based compensation expense is summarized as follows: Three Months Ended September 30, Nine Months Ended September 30, 2018 2017 2018 2017 (In thousands) Time-Based LTIP Units $ 2,520 $ 885 $ 7,772 $ 885 Performance-Based LTIP Units 1,391 469 3,898 469 LTIP Units — — 794 — Other equity awards 989 232 2,693 1,526 Share-based compensation expense - other 4,900 1,586 15,157 2,880 Formation Awards 1,375 3,963 4,192 3,963 LTIP and OP Units (1) 7,012 10,482 22,720 10,482 Share-based compensation related to Formation Transaction (2) 8,387 14,445 26,912 14,445 Total share-based compensation expense 13,287 16,031 42,069 17,325 Less amount capitalized (873 ) (161 ) (2,379 ) (161 ) Share-based compensation expense $ 12,414 $ 15,870 $ 39,690 $ 17,164 ______________________________________________ (1) Represents share-based compensation expense for LTIP Units and OP Units subject to post-Combination employment obligations. (2) Included in "General and administrative expense: Share-based compensation related to Formation Transaction" in the accompanying statements of operations. As of September 30, 2018 , we had $107.2 million of total unrecognized compensation expense related to unvested share-based payment arrangements (unvested OP Units, Formation Awards, Time-Based LTIP Units and Performance-Based LTIP Units). This expense is expected to be recognized over a weighted average period of 2.6 years.

Interest Expense Interest Expen

Interest Expense Interest Expense	9 Months Ended
	Sep. 30, 2018
Interest Expense [Abstract]
Interest Income and Interest Expense Disclosure [Text Block]	Interest Expense The following is a summary of interest expense included in the statements of operations: Three Months Ended September 30, Nine Months Ended September 30, 2018 2017 2018 2017 (In thousands) Interest expense $ 23,465 $ 16,378 $ 69,024 $ 45,011 Amortization of deferred financing costs 1,043 739 3,501 1,527 Net loss (gain) on derivative financial instruments Net unrealized 287 (467 ) (1,264 ) (467 ) Net realized (135 ) 27 (135 ) 27 Capitalized interest (5,681 ) (1,368 ) (14,863 ) (2,285 ) Interest expense $ 18,979 $ 15,309 $ 56,263 $ 43,813

Earnings (Loss) Per Common Shar

Earnings (Loss) Per Common Share	9 Months Ended
	Sep. 30, 2018
Earnings Per Share [Abstract]
Earnings (Loss) Per Common Share	Earnings (Loss) Per Common Share The following summarizes the calculation of basic and diluted earnings per common share and provides a reconciliation of the amounts of net income (loss) available to common shareholders used in calculating basic and diluted earnings per common share: Three Months Ended September 30, Nine Months Ended September 30, 2018 2017 2018 2017 (In thousands, except per share amounts) Net income (loss) $ 26,382 $ (77,991 ) $ 45,619 $ (60,332 ) Net (income) loss attributable to redeemable noncontrolling (3,552 ) 8,160 (6,532 ) 2,481 Net loss attributable to noncontrolling interests — — 127 — Net income (loss) attributable to common shareholders 22,830 (69,831 ) 39,214 (57,851 ) Distributions to participating securities (153 ) — (527 ) — Net income (loss) available to common shareholders — basic and diluted $ 22,677 $ (69,831 ) $ 38,687 $ (57,851 ) Weighted average number of common shares outstanding — basic and diluted (1) 119,835 114,744 118,588 105,347 Earnings (loss) per common share: Basic $ 0.19 $ (0.61 ) $ 0.33 $ (0.55 ) Diluted $ 0.19 $ (0.61 ) $ 0.33 $ (0.55 ) ______________ (1) For the three and nine months ended September 30, 2017 , reflects the weighted average common shares attributable to the Vornado Included Assets at the date of the Separation. The effect of the redemption of OP Units that were outstanding as of September 30, 2018 is excluded in the computation of basic and diluted earnings per common share, as the assumed exchange of such units for common shares on a one-for-one basis was antidilutive (the assumed redemption of these units would have no impact on the determination of diluted earnings per share). Since vested and outstanding OP Units, which are held by noncontrolling interests, are attributed gains and losses at an identical proportion to the common shareholders, the gains and losses attributable and their equivalent weighted average OP Unit impact are excluded from net income (loss) available to common shareholders and from the weighted average number of common shares outstanding in calculating basic and diluted earnings per common share. Performance-Based LTIP Units and Formation Awards, which totaled 3.9 million and 3.8 million for the three and nine months ended September 30, 2018 and 2.6 million and 900,000 for the three and nine months ended September 30, 2017 , were excluded from the calculation of diluted earnings per common share as they were antidilutive, but potentially could be dilutive in the future.

Fair Value Measurements

Fair Value Measurements	9 Months Ended
	Sep. 30, 2018
Fair Value Disclosures [Abstract]
Fair Value Measurements	Fair Value Measurements Financial Assets and Liabilities Measured at Fair Value on a Recurring Basis To manage or hedge our exposure to interest rate risk, we follow established risk management policies and procedures, including the use of a variety of derivative financial instruments. We do not enter into derivative financial instruments for speculative purposes. As of September 30, 2018 , we had various derivative financial instruments consisting of interest rate swap and cap agreements that are measured at fair value on a recurring basis. The net unrealized gain on our derivative financial instruments designated as cash flow hedges was $27.8 million as of September 30, 2018 and was recorded in "Accumulated other comprehensive income" in the balance sheet, of which a portion was reclassified to "Redeemable noncontrolling interests." Within the next 12 months, we expect to reclassify $4.6 million as a decrease to interest expense. The net unrealized (loss) gain on our derivative financial instruments not designated as cash flow hedges was $(287,000) and $1.3 million for the three and nine months ended September 30, 2018 and is recorded in "Interest expense" in our statements of operations. The net unrealized gain on our interest rate swaps and caps was $467,000 for both the three and nine months ended September 30, 2017 and are included in "Interest expense" in our statements of operations. ASC 820, Fair Value Measurement and Disclosures, establishes a fair value hierarchy that prioritizes observable and unobservable inputs used to measure fair value into three levels: Level 1 — quoted prices (unadjusted) in active markets that are accessible at the measurement date for assets or liabilities; Level 2 — observable prices that are based on inputs not quoted in active markets, but corroborated by market data; and Level 3 — unobservable inputs that are used when little or no market data is available. The fair values of the derivative financial instruments are based on the estimated amounts we would receive or pay to terminate the contracts at the reporting date and are determined using interest rate pricing models and observable inputs. The derivative financial instruments are classified within Level 2 of the valuation hierarchy. The following are assets and liabilities measured at fair value on a recurring basis: Fair Value Measurements Total Level 1 Level 2 Level 3 September 30, 2018 (In thousands) Derivative financial instruments designated as cash flow hedges: Classified as assets in "Other assets, net" $ 21,119 $ — $ 21,119 $ — Classified as liabilities in "Other liabilities, net" 954 — 954 — Derivative financial instruments not designated as cash flow hedges: Classified as assets in "Other assets, net" 7,237 — 7,237 — December 31, 2017 Derivative financial instruments designated as cash flow hedges: Classified as assets in "Other assets, net" $ 1,506 $ — $ 1,506 $ — Classified as liabilities in "Other liabilities, net" 2,640 — 2,640 — Derivative financial instruments not designated as cash flow hedges: Classified as assets in "Other assets, net" 635 — 635 — Classified as liabilities in "Other liabilities, net" 22 — 22 — The fair values of our derivative financial instruments were determined using widely accepted valuation techniques, including discounted cash flow analysis on the expected cash flows of the derivative financial instrument. This analysis reflected the contractual terms of the derivative, including the period to maturity, and used observable market-based inputs, including interest rate market data and implied volatilities in such interest rates. While it was determined that the majority of the inputs used to value the derivatives fall within Level 2 of the fair value hierarchy under authoritative accounting guidance, the credit valuation adjustments associated with the derivatives also utilized Level 3 inputs, such as estimates of current credit spreads to evaluate the likelihood of default. However, as of September 30, 2018 , the significance of the impact of the credit valuation adjustments on the overall valuation of the derivative financial instruments was assessed and it was determined that these adjustments were not significant to the overall valuation of the derivative financial instruments. As a result, it was determined that the derivative financial instruments in their entirety should be classified in Level 2 of the fair value hierarchy. The net unrealized gain included in "Other comprehensive income'' was primarily attributable to the net change in unrealized gains or losses related to the interest rate swaps that were outstanding as of September 30, 2018 , none of which were reported in the statements of operations because they were documented and qualified as hedging instruments. Financial Assets and Liabilities Not Measured at Fair Value As of September 30, 2018 and December 31, 2017 , all financial instruments and liabilities were reflected in our balance sheets at amounts which, in our estimation, reasonably approximated their fair values, except for the following: September 30, 2018 December 31, 2017 Carrying Amount (1) Fair Value Carrying Amount (1) Fair Value (In thousands) Financial liabilities: Mortgages payable $ 1,773,979 $ 1,785,978 $ 2,035,959 $ 2,060,899 Revolving credit facility — — 115,751 115,768 Unsecured term loans 300,000 300,307 50,000 50,029 ______________________________________ ( 1) The carrying amount consists of principal only. The fair value of our mortgages payable is estimated by discounting the future contractual cash flows of these instruments using current risk-adjusted rates available to borrowers with similar credit profiles based on market sources. The fair value of the mortgages payable was determined using Level 2 inputs of the fair value hierarchy. The fair value of our revolving credit facility and unsecured term loans is calculated based on the net present value of payments over the term of the facilities using estimated market rates for similar notes and remaining terms. The fair value of the revolving credit facility and unsecured term loans was determined using Level 2 inputs of the fair value hierarchy.

Segment Information

Segment Information	9 Months Ended
	Sep. 30, 2018
Segment Reporting [Abstract]
Segment Information	Segment Information We review operating and financial data for each property on an individual basis; therefore, each of our individual properties is a separate operating segment. Our reportable segments are aligned with our method of internal reporting and the way our Chief Executive Officer, who is also our Chief Operating Decision Maker ("CODM"), makes key operating decisions, evaluates financial results, allocates resources and manages our business. Accordingly, we aggregate our operating segments into three reportable segments (office, multifamily, and third-party real estate services) based on the economic characteristics and nature of our assets and services. The CODM measures and evaluates the performance of our operating segments, with the exception of the third-party real estate services business, based on the net operating income ("NOI") of properties within each segment. NOI includes property rental revenues and tenant reimbursements and deducts property operating expenses and real estate taxes. With respect to the third-party real estate services business, the CODM reviews revenues streams generated by this segment ("Third-party real estate services, including reimbursements"), as well as the expenses attributable to the segment ("General and administrative: third-party real estate services"), which are disclosed separately in the statements of operations. Management company assets primarily consist of management and leasing contracts with a net book value of $40.4 million and $45.7 million and classified in "Other assets, net" in the balance sheets as of September 30, 2018 and December 31, 2017 . Consistent with internal reporting presented to our CODM and our definition of NOI, the third-party real estate services operating results are excluded from the NOI data below. The following table reflects the reconciliation of net income (loss) attributable to common shareholders to consolidated NOI: Three Months Ended September 30, Nine Months Ended September 30, 2018 2017 2018 2017 (In thousands) Net income (loss) attributable to common shareholders $ 22,830 $ (69,831 ) $ 39,214 $ (57,851 ) Add: Depreciation and amortization expense 46,603 43,951 143,880 109,726 General and administrative expense: Corporate and other 12,415 10,593 37,759 35,536 Third-party real estate services 20,754 21,178 64,552 30,362 Share-based compensation related to Formation Transaction 8,387 14,445 26,912 14,445 Transaction and other costs 4,126 104,095 12,134 115,173 Interest expense 18,979 15,309 56,263 43,813 Loss on extinguishment of debt 79 689 4,536 689 Reduction of gain (gain) on bargain purchase — (27,771 ) 7,606 (27,771 ) Income tax benefit (841 ) (1,034 ) (1,436 ) (317 ) Net (income) loss attributable to redeemable noncontrolling interests 3,552 (8,160 ) 6,532 (2,481 ) Less: Third-party real estate services, including reimbursements 23,788 25,141 72,278 38,881 Other income 1,708 1,158 4,904 3,701 Income (loss) from unconsolidated real estate ventures, net 13,484 (1,679 ) 15,418 (1,365 ) Interest and other income (loss), net 4,091 (379 ) 5,177 1,366 Gain on sale of real estate 11,938 — 45,789 — Net loss attributable to noncontrolling interests — — 127 — Consolidated NOI $ 81,875 $ 79,223 $ 254,259 $ 218,741 Below is a summary of NOI by segment: Three Months Ended September 30, 2018 Office Multifamily Other Elimination of Intersegment Activity Total (In thousands) Rental revenue: Property rentals $ 95,438 $ 26,167 $ 1,956 $ (358 ) $ 123,203 Tenant reimbursements 8,036 1,563 145 — 9,744 Total rental revenue 103,474 27,730 2,101 (358 ) 132,947 Rental expense: — Property operating 29,086 8,144 2,673 (5,736 ) 34,167 Real estate taxes 12,463 3,506 936 — 16,905 Total rental expense 41,549 11,650 3,609 (5,736 ) 51,072 Consolidated NOI $ 61,925 $ 16,080 $ (1,508 ) $ 5,378 $ 81,875 Three Months Ended September 30, 2017 Office Multifamily Other Elimination of Intersegment Activity Total (In thousands) Rental revenue: Property rentals $ 91,534 $ 23,397 $ 4,171 $ (2,644 ) $ 116,458 Tenant reimbursements 7,917 1,548 128 — 9,593 Total rental revenue 99,451 24,945 4,299 (2,644 ) 126,051 Rental expense: Property operating 27,000 6,796 3,502 (7,664 ) 29,634 Real estate taxes 13,038 2,952 1,204 — 17,194 Total rental expense 40,038 9,748 4,706 (7,664 ) 46,828 Consolidated NOI $ 59,413 $ 15,197 $ (407 ) $ 5,020 $ 79,223 Nine Months Ended September 30, 2018 Office Multifamily Other Elimination of Intersegment Activity Total (In thousands) Rental revenue: Property rentals $ 294,238 $ 75,644 $ 6,068 $ (856 ) $ 375,094 Tenant reimbursements 23,480 4,778 393 — 28,651 Total rental revenue 317,718 80,422 6,461 (856 ) 403,745 Rental expense: — Property operating 83,666 22,844 5,416 (16,464 ) 95,462 Real estate taxes 39,429 10,561 4,034 — 54,024 Total rental expense 123,095 33,405 9,450 (16,464 ) 149,486 Consolidated NOI $ 194,623 $ 47,017 $ (2,989 ) $ 15,608 $ 254,259 Nine Months Ended September 30, 2017 Office Multifamily Other Elimination of Intersegment Activity Total (In thousands) Rental revenue: Property rentals $ 249,532 $ 62,050 $ 9,623 $ (4,306 ) $ 316,899 Tenant reimbursements 22,738 3,772 651 — 27,161 Total rental revenue 272,270 65,822 10,274 (4,306 ) 344,060 Rental expense: — Property operating 71,377 16,716 11,330 (22,082 ) 77,341 Real estate taxes 37,185 7,973 2,820 — 47,978 Total rental expense 108,562 24,689 14,150 (22,082 ) 125,319 Consolidated NOI $ 163,708 $ 41,133 $ (3,876 ) $ 17,776 $ 218,741 The following is a summary of certain balance sheet data by segment: Office Multifamily Other Elimination of Intersegment Activity Total September 30, 2018 (In thousands) Real estate, at cost $ 3,420,068 $ 1,599,912 $ 673,565 $ — $ 5,693,545 Investments in and advances to unconsolidated real estate ventures 211,301 105,028 44,685 — 361,014 Total assets (1) 3,488,847 1,475,233 1,211,537 (164,423 ) 6,011,194 December 31, 2017 Real estate, at cost $ 3,953,314 $ 1,476,423 $ 587,767 $ — $ 6,017,504 Investments in and advances to 124,659 98,835 38,317 — 261,811 Total assets (1) 3,542,977 1,434,999 1,299,085 (205,254 ) 6,071,807 __________________________ (1) Includes assets held for sale of $137.5 million ( $130.8 million in our office segment, $2.2 million in our multifamily segment and $4.5 million in our other segment) as of September 30, 2018 and $8.3 million ( $1.7 million in our office segment and $6.6 million in our other segment) as of December 31, 2017 .

Commitments and Contingencies

Commitments and Contingencies	9 Months Ended
	Sep. 30, 2018
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	Commitments and Contingencies Insurance We maintain general liability insurance with limits of $200.0 million per occurrence and in the aggregate, and property and rental value insurance coverage with limits of $2.0 billion per occurrence, with sub-limits for certain perils such as floods and earthquakes on each of our properties. We also maintain coverage, through our wholly owned captive insurance subsidiary, for both terrorist acts and for nuclear, biological, chemical or radiological terrorism events with limits of $2.0 billion per occurrence. These policies are partially reinsured by third-party insurance providers. We will continue to monitor the state of the insurance market and the scope and costs of coverage for acts of terrorism. We cannot anticipate what coverage will be available on commercially reasonable terms in the future. We are responsible for deductibles and losses in excess of the insurance coverage, which could be material. Our debt, consisting of mortgage loans secured by our properties, revolving credit facility and unsecured term loans contain customary covenants requiring adequate insurance coverage. Although we believe that we currently have adequate insurance coverage, we may not be able to obtain an equivalent amount of coverage at reasonable costs in the future. If lenders insist on greater coverage than we are able to obtain, it could adversely affect the ability to finance or refinance our properties. Construction Commitments As of September 30, 2018 , we have construction in progress that will require an additional $396.2 million to complete ( $310.8 million related to our consolidated entities and $85.4 million related to our unconsolidated real estate ventures at our share), based on our current plans and estimates, which we anticipate will be primarily expended over the next two to three years. These capital expenditures are generally due as the work is performed, and we expect to finance them with debt proceeds, proceeds from asset recapitalizations and sales, and available cash. Environmental Matters Each of our properties has been subjected to varying degrees of environmental assessment at various times. The environmental assessments did not reveal any material environmental contamination that we believe would have a material adverse effect on our overall business, financial condition or results of operations, or that have not been anticipated and remediated during site redevelopment as required by law. Nevertheless, there can be no assurance that the identification of new areas of contamination, changes in the extent or known scope of contamination, the discovery of additional sites or changes in cleanup requirements would not result in significant cost to us. Other There are various legal actions against us in the ordinary course of business. In our opinion, the outcome of such matters will not have a material adverse effect on our financial condition, results of operations or cash flows. From time to time, we (or ventures in which we have an ownership interest) have agreed, and may in the future with respect to unconsolidated real estate ventures agree, to (1) guarantee portions of the principal, interest and other amounts in connection with their borrowings, (2) provide customary environmental indemnifications and nonrecourse carve-outs (e.g., guarantees against fraud, misrepresentation and bankruptcy) in connection with their borrowings and (3) provide guarantees to lenders and other third parties for the completion of development projects. We customarily have agreements with our outside partners whereby the partners agree to reimburse the real estate venture or us for their share of any payments made under certain of these guarantees. Amounts that may be required to be paid in future periods in relation to budget overruns or operating losses that are also included in some of our guarantees are not estimable. Guarantees (excluding environmental) terminate either upon the satisfaction of specified circumstances or repayment of the underlying debt. At times, we have agreements with our outside partners whereby we agree to reimburse our partner for their share of any payments made by them under certain guarantees. As of September 30, 2018 , the aggregate amount of our principal payment guarantees was $69.6 million for our consolidated entities and there were no principal payment guarantees for our unconsolidated real estate ventures. As of September 30, 2018 , we expect to fund additional capital to certain of our unconsolidated investments totaling $48.6 million , which we anticipate will be primarily expended over the next two to three years. In connection with the Formation Transaction, we entered into an agreement with Vornado regarding tax matters (the "Tax Matters Agreement") that provides special rules that allocate tax liabilities if the distribution of JBG SMITH shares by Vornado, together with certain related transactions, is not tax-free. Under the Tax Matters Agreement, we may be required to indemnify Vornado against any taxes and related amounts and costs resulting from a violation by us of the Tax Matters Agreement, or from the taking of certain restricted actions by us.

Transactions with Vornado and R

Transactions with Vornado and Related Parties	9 Months Ended
	Sep. 30, 2018
Related Party Transactions [Abstract]
Transactions with Vornado and Related Parties	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 three and nine months ended September 30, 2017 were $873,000 and $13.0 million . These allocated amounts are included as a component of "General and administrative expense: Corporate and other" expenses on the statement 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 three and nine months ended September 30, 2018 were $931,000 and $3.2 million . The total charges for both the three and nine months ended September 30, 2017 were approximately $912,000 . 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 three and nine months ended September 30, 2018 was $507,000 and $1.6 million . The total revenue related to these services for both the three and nine months ended September 30, 2017 was $68,000 . 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 15 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 $130,000 and $1.8 million during the three and nine months ended September 30, 2017 . 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 $365,000 and $4.1 million during the three and nine months ended September 30, 2017 . 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 of $120,000 and $1.3 million during the three and nine months ended September 30, 2017 . 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 $5.4 million and $3.6 million during the three months ended September 30, 2018 and 2017 , and $15.5 million and $9.9 million during the nine months ended September 30, 2018 and 2017 , 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 provides 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 termination of the consulting agreement. The amount due under this consulting agreement of $4.1 million was expensed in connection with the Combination. As of September 30, 2018 , the remaining liability is $1.4 million . Additionally, in March 2017, Vornado amended Mr. Schear’s employment agreement to provide for the payment of severance, bonus and post-employment services. Transactions with Real Estate Ventures We have a third-party real estate services business that provides fee-based real estate services to the JBG Legacy Funds and other third parties. 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 three and nine months ended September 30, 2018 was $8.7 million and $25.6 million . As of September 30, 2018 and December 31, 2017 , we had receivables from the JBG Legacy Funds totaling $3.1 million for both periods for third-party real estate services, including reimbursements. We rent our corporate offices from an unconsolidated real estate venture and incurred expenses totaling $1.2 million and $3.6 million during the three and nine months ended September 30, 2018 and $792,000 during the three and nine months ended September 30, 2017 , which is recorded in "General and administrative expense: Corporate and other" in our statements of operations.

Subsequent Events

Subsequent Events	9 Months Ended
	Sep. 30, 2018
Subsequent Events [Abstract]
Subsequent Events	Subsequent Events In October 2018, we sold 1233 20th Street and the out-of-service portion of Falkland Chase-North. See Note 3 for additional information. In November 2018, our Board of Trustees declared a quarterly dividend of $0.225 per common share, payable on November 26, 2018 to shareholders of record on November 13, 2018 .

Organization and Basis of Pre_2

Organization and Basis of Presentation Accounting (Policies)	9 Months Ended
	Sep. 30, 2018
Accounting Policies [Abstract]
Basis of Accounting [Text Block]	The accompanying unaudited condensed consolidated and combined financial statements and notes are prepared in accordance with accounting principles generally accepted in the United States of America ("GAAP") for interim financial information and with the instructions of Form 10-Q and Article 10 of Regulation S-X. Accordingly, these unaudited condensed consolidated and combined financial statements do not contain certain information required in annual financial statements and notes as required under GAAP. In our opinion, all adjustments considered necessary for a fair presentation have been included, and all such adjustments are of a normal recurring nature. All intercompany transactions and balances have been eliminated. The results of operations for the three and nine months ended September 30, 2018 and 2017 are not necessarily indicative of the results that may be expected for a full year. These condensed consolidated and combined financial statements should be read in conjunction with our Annual Report on Form 10-K for the year ended December 31, 2017 , filed with the Securities and Exchange Commission. The accompanying condensed consolidated and combined financial statements include the accounts of JBG SMITH and our wholly owned subsidiaries and those other entities, including JBG SMITH LP, in which we have a controlling financial interest, including where we have been determined to be the primary beneficiary of a variable interest entity ("VIE"). See Note 5 for additional information on our VIEs. The portions of the equity and net income of consolidated subsidiaries that are not attributable to JBG SMITH are presented separately as amounts attributable to noncontrolling interests in our condensed consolidated and combined financial statements. References to the financial statements refer to our condensed consolidated and combined financial statements as of September 30, 2018 and December 31, 2017 , and for the three and nine months ended September 30, 2018 and 2017 . References to the balance sheets refer to our condensed consolidated balance sheets as of September 30, 2018 and December 31, 2017 . References to the statements of operations refer to our condensed consolidated and combined statements of operations for the three and nine months ended September 30, 2018 and 2017 . References to the statements of cash flows refer to our condensed consolidated and combined statements of cash flows for the nine months ended September 30, 2018 and 2017 .
Business Combinations Policy [Policy Text Block]	JBG SMITH and the Vornado Included Assets were under common control of Vornado for all periods prior to the Separation. The transfer of the Vornado Included Assets from Vornado to JBG SMITH was completed prior to the Separation, at net book values (historical carrying amounts) carved out from Vornado’s books and records. For purposes of the formation of JBG SMITH, the Vornado Included Assets were designated as the predecessor and the accounting acquirer of the JBG Assets. Consequently, the financial statements of JBG SMITH, as set forth herein, represent a continuation of the financial information of the Vornado Included Assets as the predecessor and accounting acquirer such that the historical financial information included herein as of any date or for any periods on or prior to the completion of the Combination represents the pre-Combination financial information of the Vornado Included Assets. The financial statements reflect the common shares as of the date of the Separation as outstanding for all periods prior to July 17, 2017. The acquisition of the JBG Assets completed subsequently by JBG SMITH was accounted for as a business combination using the acquisition method whereby identifiable assets acquired and liabilities assumed are recorded at acquisition-date fair values and income and cash flows from the operations were consolidated into the financial statements of JBG SMITH commencing July 18, 2017. Consequently, the financial statements for the periods before and after the Formation Transaction are not directly comparable. The accompanying financial statements as of September 30, 2018 and December 31, 2017 and for the three and nine months ended September 30, 2018 include our consolidated accounts. The results of operations for the three and nine months ended September 30, 2017 reflect the aggregate operations and changes in cash flows and equity on a combined basis for all periods prior to July 17, 2017 and on a consolidated basis for all periods subsequent to July 17, 2017. Therefore, our results of operations, cash flows and financial condition set forth in this report for the three and nine months ended September 30, 2017 are not necessarily indicative of our future results of operations, cash flows or financial condition as an independent, publicly traded company. The historical financial results for the Vornado Included Assets reflect charges for certain corporate costs allocated by the former parent, which were based on either actual costs incurred or a proportion of costs estimated to be applicable, to the Vornado Included Assets based on an analysis of key metrics, including total revenues. Such costs do not necessarily reflect what the actual costs would have been if JBG SMITH had been operating as a separate standalone public company. See Note 16 for additional information.

Summary of Significant Accoun_2

Summary of Significant Accounting Policies (Policies)	9 Months Ended
	Sep. 30, 2018
Accounting Policies [Abstract]
Use of Estimates, Policy [Policy Text Block]	The preparation of the financial statements in conformity with GAAP requires us to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities as of the date of the financial statements and the reported amounts of revenue and expenses during the reporting period. The most significant of these estimates include: (i) the underlying cash flows used to establish the fair values recorded in connection with the Combination and used in assessing impairment and (ii) the determination of useful lives for tangible and intangible assets. Actual results could differ from these estimates.
New Accounting Pronouncements, Policy [Policy Text Block]	The following table provides a brief description of recent accounting pronouncements by the Financial Accounting Standards Board ("FASB") that could have a material effect on our financial statements: Standard Description Date of Adoption Effect on the Financial Statements or Other Significant Matters Standard adopted ASU 2014-09, Revenue from Contracts with Customers (Topic 606), as clarified and amended by ASU 2016-08, ASU 2016-10 and ASU 2016-12 This standard establishes a single comprehensive model for entities to use in accounting for revenue arising from contracts with customers and supersedes most of the existing revenue recognition guidance. It requires an entity to recognize revenue when it transfers promised goods or services to customers in an amount that reflects the consideration to which the entity expects to be entitled in exchange for those goods or services and also requires certain additional disclosures. January 2018 We utilized the modified retrospective method of adoption. The standard excludes from its scope the areas of accounting that most significantly affect our revenue recognition, including accounting for leases and financial instruments. Our evaluation determined there were no required changes to our recognition of revenue related to our third-party real estate services, tenant reimbursements, property and asset management fees, or transactional/management fees for leasing, development and construction. Our evaluation also determined there were no required changes to our recognition of promote fees and dispositions of real estate properties as we did not have any deferred gains due to continuing involvement at the time of adoption. Therefore, the adoption of this standard did not have a material impact on our financial statements. We adopted the practical expedient of this standard to only assess the recognition of revenue for open contracts at the date of adoption and there was no adjustment to the opening balance of our accumulated deficit at January 1, 2018. The comparative information has not been restated and continues to be reported under the accounting standards in effect for that period. Standard Description Date of Adoption Effect on the Financial Statements or Other Significant Matters Standards not yet adopted ASU 2016-02, Leases (Topic 842), as clarified and amended by ASU 2018-01, ASU 2018-10 and ASU 2018-11 This standard establishes principles for the recognition, measurement, presentation and disclosure of leases for both lessees and lessors. ASU 2016-02 requires lessees to apply a dual approach, classifying leases as either finance or operating leases based on the principle of whether or not the lease is effectively a financed purchase. Lessees are required to record a right-of-use asset and a lease liability for all leases with a term of greater than 12 months. Leases with a term of 12 months or less will be accounted for similar to existing guidance for operating leases. Lessees will recognize expense based on the effective interest method for finance leases or on a straight-line basis for operating leases. The ASU also clarifies that an assessment of whether a land easement meets the definition of a lease under the new lease standard is required. The provisions of this standard are effective for fiscal years beginning after December 15, 2018 and should be applied through a modified retrospective transition, which includes optional practical expedients related to leases that commenced before the effective date and allows the new requirements to be applied on the date of adoption rather than the beginning of the earliest comparative period presented. January 2019 We are currently evaluating the overall impact of the adoption of ASU 2016-02 on our financial statements. ASU 2016-02 will more significantly impact the accounting for leases in which we are the lessee. We have ground leases for which we will be required to record a right-of-use asset and lease liability equal to the present value of the remaining minimum lease payments upon adoption of this standard. As of September 30, 2018, future ground lease payments totaled $573.9 million to which we would apply a discount rate. We are in the process of determining an appropriate discount rate. Under ASU 2016-02, initial direct costs for both lessees and lessors would include only those costs that are incremental to the arrangement and would not have been incurred if the lease had not been obtained. As a result, we will no longer be able to capitalize internal leasing costs and instead will be required to expense these costs as incurred. Capitalized internal leasing costs were $1.5 million and $1.0 million for the three months ended September 30, 2018 and 2017, and $4.3 million and $1.8 million for the nine months ended September 30, 2018 and 2017. We will apply the modified retrospective approach of adoption and anticipate electing the package of practical expedients that allows an entity to not reassess (i) whether any expired or existing contracts are or contain leases, (ii) lease classifications for any expired or existing leases and (iii) initial direct costs for any expired or existing leases. ASU 2018-09, Codification Improvements These amendments provide clarifications and corrections to certain ASC subtopics including the following: 220-10 (Income Statement - Reporting Comprehensive Income - Overall), 470-50 (Debt - Modifications and Extinguishments), 480-10 (Distinguishing Liabilities from Equity - Overall), 718-740 (Compensation - Stock Compensation - Income Taxes), 805-740 (Business Combinations - Income Taxes), 815-10 (Derivatives and Hedging - Overall), and 820-10 (Fair Value Measurement - Overall). January 2019 The updates related to Subtopics 470-50 and 820-10 were effective immediately and their adoption did not have an impact on our financial statements. We are currently evaluating the remaining guidance to determine the impact it may have on our financial statements.

Organization and Basis of Pre_3

Organization and Basis of Presentation (Tables)	9 Months Ended
	Sep. 30, 2018
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Business Acquisition, Pro Forma Information [Table Text Block]	The pro forma information was adjusted to exclude transaction and other costs of $104.1 million and $115.2 million for the three and nine months ended September 30, 2017 . Three Months Ended Nine Months Ended September 30, 2017 (In thousands) Pro forma information: Total revenue $ 160,428 $ 481,314 Net income (loss) attributable to common shareholders 2,283 (13,741 )

Summary of Significant Accoun_3

Summary of Significant Accounting Policies (Tables)	9 Months Ended
	Sep. 30, 2018
Accounting Policies [Abstract]
Schedule of Recent Accounting Pronouncements	The following table provides a brief description of recent accounting pronouncements by the Financial Accounting Standards Board ("FASB") that could have a material effect on our financial statements: Standard Description Date of Adoption Effect on the Financial Statements or Other Significant Matters Standard adopted ASU 2014-09, Revenue from Contracts with Customers (Topic 606), as clarified and amended by ASU 2016-08, ASU 2016-10 and ASU 2016-12 This standard establishes a single comprehensive model for entities to use in accounting for revenue arising from contracts with customers and supersedes most of the existing revenue recognition guidance. It requires an entity to recognize revenue when it transfers promised goods or services to customers in an amount that reflects the consideration to which the entity expects to be entitled in exchange for those goods or services and also requires certain additional disclosures. January 2018 We utilized the modified retrospective method of adoption. The standard excludes from its scope the areas of accounting that most significantly affect our revenue recognition, including accounting for leases and financial instruments. Our evaluation determined there were no required changes to our recognition of revenue related to our third-party real estate services, tenant reimbursements, property and asset management fees, or transactional/management fees for leasing, development and construction. Our evaluation also determined there were no required changes to our recognition of promote fees and dispositions of real estate properties as we did not have any deferred gains due to continuing involvement at the time of adoption. Therefore, the adoption of this standard did not have a material impact on our financial statements. We adopted the practical expedient of this standard to only assess the recognition of revenue for open contracts at the date of adoption and there was no adjustment to the opening balance of our accumulated deficit at January 1, 2018. The comparative information has not been restated and continues to be reported under the accounting standards in effect for that period. Standard Description Date of Adoption Effect on the Financial Statements or Other Significant Matters Standards not yet adopted ASU 2016-02, Leases (Topic 842), as clarified and amended by ASU 2018-01, ASU 2018-10 and ASU 2018-11 This standard establishes principles for the recognition, measurement, presentation and disclosure of leases for both lessees and lessors. ASU 2016-02 requires lessees to apply a dual approach, classifying leases as either finance or operating leases based on the principle of whether or not the lease is effectively a financed purchase. Lessees are required to record a right-of-use asset and a lease liability for all leases with a term of greater than 12 months. Leases with a term of 12 months or less will be accounted for similar to existing guidance for operating leases. Lessees will recognize expense based on the effective interest method for finance leases or on a straight-line basis for operating leases. The ASU also clarifies that an assessment of whether a land easement meets the definition of a lease under the new lease standard is required. The provisions of this standard are effective for fiscal years beginning after December 15, 2018 and should be applied through a modified retrospective transition, which includes optional practical expedients related to leases that commenced before the effective date and allows the new requirements to be applied on the date of adoption rather than the beginning of the earliest comparative period presented. January 2019 We are currently evaluating the overall impact of the adoption of ASU 2016-02 on our financial statements. ASU 2016-02 will more significantly impact the accounting for leases in which we are the lessee. We have ground leases for which we will be required to record a right-of-use asset and lease liability equal to the present value of the remaining minimum lease payments upon adoption of this standard. As of September 30, 2018, future ground lease payments totaled $573.9 million to which we would apply a discount rate. We are in the process of determining an appropriate discount rate. Under ASU 2016-02, initial direct costs for both lessees and lessors would include only those costs that are incremental to the arrangement and would not have been incurred if the lease had not been obtained. As a result, we will no longer be able to capitalize internal leasing costs and instead will be required to expense these costs as incurred. Capitalized internal leasing costs were $1.5 million and $1.0 million for the three months ended September 30, 2018 and 2017, and $4.3 million and $1.8 million for the nine months ended September 30, 2018 and 2017. We will apply the modified retrospective approach of adoption and anticipate electing the package of practical expedients that allows an entity to not reassess (i) whether any expired or existing contracts are or contain leases, (ii) lease classifications for any expired or existing leases and (iii) initial direct costs for any expired or existing leases. ASU 2018-09, Codification Improvements These amendments provide clarifications and corrections to certain ASC subtopics including the following: 220-10 (Income Statement - Reporting Comprehensive Income - Overall), 470-50 (Debt - Modifications and Extinguishments), 480-10 (Distinguishing Liabilities from Equity - Overall), 718-740 (Compensation - Stock Compensation - Income Taxes), 805-740 (Business Combinations - Income Taxes), 815-10 (Derivatives and Hedging - Overall), and 820-10 (Fair Value Measurement - Overall). January 2019 The updates related to Subtopics 470-50 and 820-10 were effective immediately and their adoption did not have an impact on our financial statements. We are currently evaluating the remaining guidance to determine the impact it may have on our financial statements.

Investments in and Advances t_2

Investments in and Advances to Unconsolidated Real Estate Ventures (Tables)	9 Months Ended
	Sep. 30, 2018
Equity Method Investments and Joint Ventures [Abstract]
Composition of Investments	The following is a summary of the debt of our unconsolidated real estate ventures: Weighted Average Effective (1) September 30, 2018 December 31, 2017 (In thousands) Variable rate (2) 4.96% $ 536,950 $ 534,500 Fixed rate (3) 3.95% 852,674 657,701 Unconsolidated real estate ventures - mortgages payable 1,389,624 1,192,201 Unamortized deferred financing costs (2,555 ) (2,000 ) Unconsolidated real estate ventures - mortgages payable, net (4) $ 1,387,069 $ 1,190,201 ______________ (1) Weighted average effective interest rate as of September 30, 2018 . (2) Includes variable rate mortgages payable with interest rate cap agreements. (3) Includes variable rate mortgages payable with interest rates fixed by interest rate swap agreements. (4) See Note 15 for additional information on guarantees of the debt of certain of our unconsolidated real estate ventures. The following is a summary of the financial information for our unconsolidated real estate ventures: September 30, 2018 December 31, 2017 Combined balance sheet information: (In thousands) Real estate, net $ 2,425,633 $ 2,106,670 Other assets, net 307,105 264,731 Total assets $ 2,732,738 $ 2,371,401 Mortgages payable, net $ 1,387,069 $ 1,190,201 Other liabilities, net 100,104 76,416 Total liabilities 1,487,173 1,266,617 Total equity 1,245,565 1,104,784 Total liabilities and equity $ 2,732,738 $ 2,371,401 Three Months Ended September 30, Nine Months Ended September 30, 2018 2017 2018 2017 Combined income statement information: (In thousands) Total revenue $ 76,247 $ 46,830 $ 236,938 $ 83,387 Operating income 6,861 3,237 23,719 14,576 Net loss (6,970 ) (5,191 ) (12,159 ) (414 ) The following is a summary of the composition of our investments in and advances to unconsolidated real estate ventures: Real Estate Venture Partners Ownership Interest (1) September 30, 2018 December 31, 2017 (In thousands) Canadian Pension Plan Investment Board ("CPPIB") 55.0% - 79.2% $ 136,877 $ 36,317 Landmark 1.8% - 49.0% 86,561 95,368 CBREI Venture 5.0% - 64.0% 75,713 79,062 Berkshire Group 50.0% 38,124 27,761 Brandywine 30.0% 13,858 13,741 CIM Group ("CIM") and Pacific Life Insurance Company ("PacLife") 16.7% 9,664 — JP Morgan —% — 9,296 Other 137 246 Total investments in unconsolidated real estate ventures 360,934 261,791 Advances to unconsolidated real estate ventures 80 20 Total investments in and advances to unconsolidated real estate ventures $ 361,014 $ 261,811 _______________ (1) Ownership interests as of September 30, 2018 . We have multiple investments with certain venture partners with varying ownership interests.

Other Assets, Net (Tables)

Other Assets, Net (Tables)	9 Months Ended
	Sep. 30, 2018
Deferred Costs, Capitalized, Prepaid, and Other Assets Disclosure [Abstract]
Summary of Other Assets, net	The following is a summary of other assets, net: September 30, 2018 December 31, 2017 (In thousands) Deferred leasing costs $ 189,959 $ 171,153 Accumulated amortization (72,217 ) (67,180 ) Deferred leasing costs, net 117,742 103,973 Prepaid expenses 14,623 9,038 Identified intangible assets, net 94,221 126,467 Deferred financing costs on credit facility, net 5,292 6,654 Deposits 3,592 6,317 Derivative agreements, at fair value 28,356 2,141 Other 18,132 9,333 Total other assets, net $ 281,958 $ 263,923

Debt (Tables)

Debt (Tables)	9 Months Ended
	Sep. 30, 2018
Debt Disclosure [Abstract]
Summary of Debt	The following is a summary of amounts outstanding under the credit facility: Interest Rate (1) September 30, 2018 December 31, 2017 (In thousands) Revolving credit facility (2) (3) (4) (5) 3.36% $ — $ 115,751 Tranche A-1 Term Loan 3.32% $ 100,000 $ 50,000 Tranche A-2 Term Loan 3.81% 200,000 — Unsecured term loans 300,000 50,000 Unamortized deferred financing costs, net (3,019 ) (3,463 ) Unsecured term loans, net $ 296,981 $ 46,537 __________________________ (1) Interest rate as of September 30, 2018 . (2) As of September 30, 2018 and December 31, 2017 , letters of credit with an aggregate face amount of $5.7 million were provided under our revolving credit facility. The following is a summary of mortgages payable: Weighted Average (1) September 30, 2018 December 31, 2017 (In thousands) Variable rate (2) 4.16% $ 182,996 $ 498,253 Fixed rate (3) (4) 4.19% 1,590,983 1,537,706 Mortgages payable 1,773,979 2,035,959 Unamortized deferred financing costs and premium/ discount, net (4,041 ) (10,267 ) Mortgages payable, net $ 1,769,938 $ 2,025,692 __________________________ (1) Weighted average effective interest rate as of September 30, 2018 . (2) Includes variable rate mortgages payable with interest rate cap agreements. (3) Includes variable rate mortgages payable with interest rates fixed by interest rate swap agreements.

Other Liabilities, Net (Tables)

Other Liabilities, Net (Tables)	9 Months Ended
	Sep. 30, 2018
Other Liabilities Disclosure [Abstract]
Composition of Other Liabilities, Net	The following is a summary of other liabilities, net: September 30, 2018 December 31, 2017 (In thousands) Lease intangible liabilities $ 40,179 $ 44,917 Accumulated amortization (25,523 ) (26,950 ) Lease intangible liabilities, net 14,656 17,967 Prepaid rent 15,030 15,751 Lease assumption liabilities and accrued tenant incentives 49,510 50,866 Capital lease obligation 15,736 15,819 Security deposits 13,009 13,618 Ground lease deferred rent payable 3,498 3,730 Net deferred tax liability 6,446 8,202 Dividends payable (1) — 31,097 Other 1,667 4,227 Total other liabilities, net $ 119,552 $ 161,277 ________________________________________ (1) Dividends declared in December 2017 were paid in January 2018.

Redeemable Noncontrolling Int_2

Redeemable Noncontrolling Interests (Tables)	9 Months Ended
	Sep. 30, 2018
Noncontrolling Interest [Abstract]
Redeemable Noncontrolling Interests	Below is a summary of the activity of redeemable noncontrolling interests: Nine Months Ended September 30, 2018 2017 JBG SMITH LP Consolidated Real Estate Venture Total JBG SMITH LP Consolidated Real Estate Venture Total (In thousands) Balance as of beginning of period $ 603,717 $ 5,412 $ 609,129 $ — $ — $ — Fair value of OP Unit redemptions (109,208 ) — (109,208 ) — — — OP Units issued at the Separation — — — 96,632 — 96,632 OP Units issued in connection with the Combination (1) — — — 359,967 — 359,967 Net income (loss) attributable to redeemable noncontrolling interests 6,537 (5 ) 6,532 (2,481 ) — (2,481 ) Other comprehensive income 3,406 — 3,406 — — — Contributions (distributions) (8,763 ) 500 (8,263 ) — — — Share-based compensation expense 39,376 — 39,376 15,799 — 15,799 Adjustment to redemption value 21,346 — 21,346 97,084 — 97,084 Balance as of end of period $ 556,411 $ 5,907 $ 562,318 $ 567,001 $ — $ 567,001

Share-Based Payments (Tables)

Share-Based Payments (Tables)	9 Months Ended
	Sep. 30, 2018
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Summary of Share-Based Compensation Expense	Share-based compensation expense is summarized as follows: Three Months Ended September 30, Nine Months Ended September 30, 2018 2017 2018 2017 (In thousands) Time-Based LTIP Units $ 2,520 $ 885 $ 7,772 $ 885 Performance-Based LTIP Units 1,391 469 3,898 469 LTIP Units — — 794 — Other equity awards 989 232 2,693 1,526 Share-based compensation expense - other 4,900 1,586 15,157 2,880 Formation Awards 1,375 3,963 4,192 3,963 LTIP and OP Units (1) 7,012 10,482 22,720 10,482 Share-based compensation related to Formation Transaction (2) 8,387 14,445 26,912 14,445 Total share-based compensation expense 13,287 16,031 42,069 17,325 Less amount capitalized (873 ) (161 ) (2,379 ) (161 ) Share-based compensation expense $ 12,414 $ 15,870 $ 39,690 $ 17,164 ______________________________________________ (1) Represents share-based compensation expense for LTIP Units and OP Units subject to post-Combination employment obligations. (2) Included in "General and administrative expense: Share-based compensation related to Formation Transaction" in the accompanying statements of operations.

Earnings (Loss) Per Common Sh_2

Earnings (Loss) Per Common Share EPS (Tables)	9 Months Ended
	Sep. 30, 2018
Earnings Per Share [Abstract]
Schedule of Earnings Per Share, Basic and Diluted [Table Text Block]	The following summarizes the calculation of basic and diluted earnings per common share and provides a reconciliation of the amounts of net income (loss) available to common shareholders used in calculating basic and diluted earnings per common share: Three Months Ended September 30, Nine Months Ended September 30, 2018 2017 2018 2017 (In thousands, except per share amounts) Net income (loss) $ 26,382 $ (77,991 ) $ 45,619 $ (60,332 ) Net (income) loss attributable to redeemable noncontrolling (3,552 ) 8,160 (6,532 ) 2,481 Net loss attributable to noncontrolling interests — — 127 — Net income (loss) attributable to common shareholders 22,830 (69,831 ) 39,214 (57,851 ) Distributions to participating securities (153 ) — (527 ) — Net income (loss) available to common shareholders — basic and diluted $ 22,677 $ (69,831 ) $ 38,687 $ (57,851 ) Weighted average number of common shares outstanding — basic and diluted (1) 119,835 114,744 118,588 105,347 Earnings (loss) per common share: Basic $ 0.19 $ (0.61 ) $ 0.33 $ (0.55 ) Diluted $ 0.19 $ (0.61 ) $ 0.33 $ (0.55 ) ______________ (1) For the three and nine months ended September 30, 2017 , reflects the weighted average common shares attributable to the Vornado Included Assets at the date of the Separation.

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	9 Months Ended
	Sep. 30, 2018
Fair Value Disclosures [Abstract]
Schedule of Fair Value, Assets and Liabilities Measured on Recurring Basis	The following are assets and liabilities measured at fair value on a recurring basis: Fair Value Measurements Total Level 1 Level 2 Level 3 September 30, 2018 (In thousands) Derivative financial instruments designated as cash flow hedges: Classified as assets in "Other assets, net" $ 21,119 $ — $ 21,119 $ — Classified as liabilities in "Other liabilities, net" 954 — 954 — Derivative financial instruments not designated as cash flow hedges: Classified as assets in "Other assets, net" 7,237 — 7,237 — December 31, 2017 Derivative financial instruments designated as cash flow hedges: Classified as assets in "Other assets, net" $ 1,506 $ — $ 1,506 $ — Classified as liabilities in "Other liabilities, net" 2,640 — 2,640 — Derivative financial instruments not designated as cash flow hedges: Classified as assets in "Other assets, net" 635 — 635 — Classified as liabilities in "Other liabilities, net" 22 — 22 —
Schedule of Financial Instruments and Liabilities as Reflected on Balance Sheet	As of September 30, 2018 and December 31, 2017 , all financial instruments and liabilities were reflected in our balance sheets at amounts which, in our estimation, reasonably approximated their fair values, except for the following: September 30, 2018 December 31, 2017 Carrying Amount (1) Fair Value Carrying Amount (1) Fair Value (In thousands) Financial liabilities: Mortgages payable $ 1,773,979 $ 1,785,978 $ 2,035,959 $ 2,060,899 Revolving credit facility — — 115,751 115,768 Unsecured term loans 300,000 300,307 50,000 50,029 ______________________________________ ( 1) The carrying amount consists of principal only.

Segment Information (Tables)

Segment Information (Tables)	9 Months Ended
	Sep. 30, 2018
Segment Reporting [Abstract]
Segment information	The following table reflects the reconciliation of net income (loss) attributable to common shareholders to consolidated NOI: Three Months Ended September 30, Nine Months Ended September 30, 2018 2017 2018 2017 (In thousands) Net income (loss) attributable to common shareholders $ 22,830 $ (69,831 ) $ 39,214 $ (57,851 ) Add: Depreciation and amortization expense 46,603 43,951 143,880 109,726 General and administrative expense: Corporate and other 12,415 10,593 37,759 35,536 Third-party real estate services 20,754 21,178 64,552 30,362 Share-based compensation related to Formation Transaction 8,387 14,445 26,912 14,445 Transaction and other costs 4,126 104,095 12,134 115,173 Interest expense 18,979 15,309 56,263 43,813 Loss on extinguishment of debt 79 689 4,536 689 Reduction of gain (gain) on bargain purchase — (27,771 ) 7,606 (27,771 ) Income tax benefit (841 ) (1,034 ) (1,436 ) (317 ) Net (income) loss attributable to redeemable noncontrolling interests 3,552 (8,160 ) 6,532 (2,481 ) Less: Third-party real estate services, including reimbursements 23,788 25,141 72,278 38,881 Other income 1,708 1,158 4,904 3,701 Income (loss) from unconsolidated real estate ventures, net 13,484 (1,679 ) 15,418 (1,365 ) Interest and other income (loss), net 4,091 (379 ) 5,177 1,366 Gain on sale of real estate 11,938 — 45,789 — Net loss attributable to noncontrolling interests — — 127 — Consolidated NOI $ 81,875 $ 79,223 $ 254,259 $ 218,741 Below is a summary of NOI by segment: Three Months Ended September 30, 2018 Office Multifamily Other Elimination of Intersegment Activity Total (In thousands) Rental revenue: Property rentals $ 95,438 $ 26,167 $ 1,956 $ (358 ) $ 123,203 Tenant reimbursements 8,036 1,563 145 — 9,744 Total rental revenue 103,474 27,730 2,101 (358 ) 132,947 Rental expense: — Property operating 29,086 8,144 2,673 (5,736 ) 34,167 Real estate taxes 12,463 3,506 936 — 16,905 Total rental expense 41,549 11,650 3,609 (5,736 ) 51,072 Consolidated NOI $ 61,925 $ 16,080 $ (1,508 ) $ 5,378 $ 81,875 Three Months Ended September 30, 2017 Office Multifamily Other Elimination of Intersegment Activity Total (In thousands) Rental revenue: Property rentals $ 91,534 $ 23,397 $ 4,171 $ (2,644 ) $ 116,458 Tenant reimbursements 7,917 1,548 128 — 9,593 Total rental revenue 99,451 24,945 4,299 (2,644 ) 126,051 Rental expense: Property operating 27,000 6,796 3,502 (7,664 ) 29,634 Real estate taxes 13,038 2,952 1,204 — 17,194 Total rental expense 40,038 9,748 4,706 (7,664 ) 46,828 Consolidated NOI $ 59,413 $ 15,197 $ (407 ) $ 5,020 $ 79,223 Nine Months Ended September 30, 2018 Office Multifamily Other Elimination of Intersegment Activity Total (In thousands) Rental revenue: Property rentals $ 294,238 $ 75,644 $ 6,068 $ (856 ) $ 375,094 Tenant reimbursements 23,480 4,778 393 — 28,651 Total rental revenue 317,718 80,422 6,461 (856 ) 403,745 Rental expense: — Property operating 83,666 22,844 5,416 (16,464 ) 95,462 Real estate taxes 39,429 10,561 4,034 — 54,024 Total rental expense 123,095 33,405 9,450 (16,464 ) 149,486 Consolidated NOI $ 194,623 $ 47,017 $ (2,989 ) $ 15,608 $ 254,259 Nine Months Ended September 30, 2017 Office Multifamily Other Elimination of Intersegment Activity Total (In thousands) Rental revenue: Property rentals $ 249,532 $ 62,050 $ 9,623 $ (4,306 ) $ 316,899 Tenant reimbursements 22,738 3,772 651 — 27,161 Total rental revenue 272,270 65,822 10,274 (4,306 ) 344,060 Rental expense: — Property operating 71,377 16,716 11,330 (22,082 ) 77,341 Real estate taxes 37,185 7,973 2,820 — 47,978 Total rental expense 108,562 24,689 14,150 (22,082 ) 125,319 Consolidated NOI $ 163,708 $ 41,133 $ (3,876 ) $ 17,776 $ 218,741 The following is a summary of certain balance sheet data by segment: Office Multifamily Other Elimination of Intersegment Activity Total September 30, 2018 (In thousands) Real estate, at cost $ 3,420,068 $ 1,599,912 $ 673,565 $ — $ 5,693,545 Investments in and advances to unconsolidated real estate ventures 211,301 105,028 44,685 — 361,014 Total assets (1) 3,488,847 1,475,233 1,211,537 (164,423 ) 6,011,194 December 31, 2017 Real estate, at cost $ 3,953,314 $ 1,476,423 $ 587,767 $ — $ 6,017,504 Investments in and advances to 124,659 98,835 38,317 — 261,811 Total assets (1) 3,542,977 1,434,999 1,299,085 (205,254 ) 6,071,807 __________________________ (1) Includes assets held for sale of $137.5 million ( $130.8 million in our office segment, $2.2 million in our multifamily segment and $4.5 million in our other segment) as of September 30, 2018 and $8.3 million ( $1.7 million in our office segment and $6.6 million in our other segment) as of December 31, 2017 .

Organization and Basis of Pre_4

Organization and Basis of Presentation - Narrative (Details) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018USD ($)ft²building_unitproperties	Sep. 30, 2017USD ($)	Sep. 30, 2018USD ($)ft²building_unitproperties	Sep. 30, 2017USD ($)
Real Estate Properties [Line Items]
Number of real estate properties | properties	65		65
Third-party real estate services | $	$ 20,754	$ 21,178	$ 64,552	$ 30,362
Third-party real estate services, including reimbursements | $	$ 23,788	$ 25,141	$ 72,278	$ 38,881
Asset under Construction
Real Estate Properties [Line Items]
Number of real estate properties | properties	7		7
Future Development
Real Estate Properties [Line Items]
Number of real estate properties | properties	43		43
Area of real estate property (in square feet) | ft²	22,400,000		22,400,000
Office Building
Real Estate Properties [Line Items]
Number of real estate properties | properties	46		46
Area of real estate property (in square feet) | ft²	13,000,000		13,000,000
Office Building | Asset under Construction
Real Estate Properties [Line Items]
Number of real estate properties | properties	3		3
Area of real estate property (in square feet) | ft²	778,000		778,000
Multifamily
Real Estate Properties [Line Items]
Number of real estate properties | properties	15		15
Number of building units | building_unit	6,307		6,307
Multifamily | Asset under Construction
Real Estate Properties [Line Items]
Number of real estate properties | properties	4		4
Number of building units | building_unit	1,476		1,476
Other Property
Real Estate Properties [Line Items]
Number of real estate properties | properties	4		4
Area of real estate property (in square feet) | ft²	806,000		806,000
Wholly Owned Properties | Future Development
Real Estate Properties [Line Items]
Area of real estate property (in square feet) | ft²	19,000,000		19,000,000
Wholly Owned Properties | Office Building
Real Estate Properties [Line Items]
Area of real estate property (in square feet) | ft²	11,500,000		11,500,000
Wholly Owned Properties | Office Building | Asset under Construction
Real Estate Properties [Line Items]
Area of real estate property (in square feet) | ft²	546,000		546,000
Wholly Owned Properties | Multifamily
Real Estate Properties [Line Items]
Number of building units | building_unit	4,523		4,523
Wholly Owned Properties | Multifamily | Asset under Construction
Real Estate Properties [Line Items]
Number of building units | building_unit	1,284		1,284
Wholly Owned Properties | Other Property
Real Estate Properties [Line Items]
Area of real estate property (in square feet) | ft²	352,000		352,000
JBG Smith, LP
Real Estate Properties [Line Items]
Ownership interest by parent	87.80%		87.80%

Organization and Basis of Pre_5

Organization and Basis of Presentation Pro Forma Information (Details) - USD ($)	3 Months Ended			9 Months Ended
	Sep. 30, 2018	Dec. 31, 2017	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Transaction and other costs	$ 4,126,000		$ 104,095,000	$ 12,134,000	$ 115,173,000
Total revenue			160,428,000		481,314,000
Net loss attributable to common shareholders			2,283,000		(13,741,000)
Business Combination, Provisional Information, Initial Accounting Incomplete, Adjustment, Bargain Purchase, Reduction Of Gain	0	$ 3,400,000	27,771,000	(7,606,000)	27,771,000
JBG Companies
Business Combination, Provisional Information, Initial Accounting Incomplete, Adjustment, Lease Liabilities				(4,700,000)
Business Combination, Pro Forma Information, Revenue of Acquiree since Acquisition Date, Actual			34,900,000		34,900,000
Transaction and other costs	$ 4,126,000		104,095,000		115,200,000
Business Combination, Provisional Information, Initial Accounting Incomplete, Adjustment, Real Estate Investments, Unconsolidated Real Estate And Other Joint Ventures				(468,000)
Business Combination, Pro Forma Information, Earnings or Loss of Acquiree since Acquisition Date, Actual			$ 7,800,000		$ 7,800,000
Business Combination, Provisional Information, Initial Accounting Incomplete, Adjustment, Current Liabilities, Other				$ (2,400,000)

Summary of Significant Accoun_4

Summary of Significant Accounting Policies - Narrative (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Property, Plant and Equipment [Line Items]
Capitalization of internal leasing costs - QTD	$ 1.5	$ 1	$ 4.3	$ 1.8
Contractual Obligation	$ 573.9		$ 573.9

Disposals and Assets Held for_2

Disposals and Assets Held for Sale (Details) $ in Thousands	1 Months Ended			3 Months Ended		9 Months Ended
	Oct. 31, 2018USD ($)	May 31, 2018USD ($)	Apr. 30, 2018USD ($)	Sep. 30, 2018USD ($)ft²	Sep. 30, 2017USD ($)	Sep. 30, 2018USD ($)ft²	Sep. 30, 2017USD ($)	Aug. 31, 2018	Dec. 31, 2017USD ($)
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Proceeds from Sale of Property Held-for-sale						$ 358,599
Proceeds from sale of real estate						287,149
Gains (Losses) on Sales of Investment Real Estate				$ 11,938	$ 0	45,789	$ 0
Assets Held-for-sale, Not Part of Disposal Group				137,455		137,455			$ 8,293
Liabilities held for sale				$ 45,657		45,657			$ 0
Mortgages payable
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Repayments of Secured Debt						$ 251,100
Revolving credit facility
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Repayments of Secured Debt		$ 115,000
JP Morgan [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Ownership Interest				0.00%		0.00%		5.00%
Summit I and II [Member] | Mortgages payable
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Repayments of Secured Debt			$ 59,000
Disposal Group, Held-for-sale or Disposed of by Sale, Not Discontinued Operations [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Area of real estate property (in square feet) | ft²				551,418		551,418
Subsequent Event [Member] | 1233 20th Street [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Proceeds from Sale of Property Held-for-sale	$ 65,000
Subsequent Event [Member] | Falkland Chase-North [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Proceeds from Sale of Property Held-for-sale	3,800
Subsequent Event [Member] | Commerce Executive [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Proceeds from Sale of Property Held-for-sale	$ 115,000
Summit I and II, Bowen Bldg & Executive Tower [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Area of real estate property (in square feet) | ft²				645,351		645,351
Washington, D.C. [Member] | 1233 20th Street [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Area of real estate property (in square feet) | ft²				149,684		149,684
Assets Held-for-sale, Not Part of Disposal Group				$ 59,602		$ 59,602
Liabilities held for sale				$ 43,802		$ 43,802
Washington, D.C. [Member] | Bowen Building, Washington DC [Member] | Office Segment [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Area of real estate property (in square feet) | ft²				231,402		231,402
Proceeds from Sale of Property Held-for-sale						$ 140,000
Proceeds from sale of real estate						136,488
Gains (Losses) on Sales of Investment Real Estate						$ 27,207
Washington, D.C. [Member] | Executive Tower [Member] | Office Segment [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Area of real estate property (in square feet) | ft²				129,831		129,831
Proceeds from Sale of Property Held-for-sale						$ 121,445
Proceeds from sale of real estate						113,267
Gains (Losses) on Sales of Investment Real Estate						$ 11,938
Downtown Silver Spring, MD [Member] | Falkland Chase-North [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Area of real estate property (in square feet) | ft²				13,284		13,284
Assets Held-for-sale, Not Part of Disposal Group				$ 2,218		$ 2,218
Liabilities held for sale				$ 0		$ 0
Reston, Virginia [Member] | Summit I & II Land [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Area of real estate property (in square feet) | ft²				0		0
Proceeds from Sale of Property Held-for-sale						$ 2,154
Proceeds from sale of real estate						2,154
Gains (Losses) on Sales of Investment Real Estate						$ 455
Reston, Virginia [Member] | Summit I and II [Member] | Office Segment [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Area of real estate property (in square feet) | ft²				284,118		284,118
Proceeds from Sale of Property Held-for-sale						$ 95,000
Proceeds from sale of real estate						35,240
Gains (Losses) on Sales of Investment Real Estate						$ 6,189
Reston, Virginia [Member] | Commerce Executive [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Area of real estate property (in square feet) | ft²				388,450		388,450
Assets Held-for-sale, Not Part of Disposal Group				$ 75,635		$ 75,635
Liabilities held for sale				$ 1,855		$ 1,855

Investments in and Advances t_3

Investments in and Advances to Unconsolidated Real Estate Ventures - Summary of Composition of Investments (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Aug. 31, 2018	Jan. 31, 2018	Dec. 31, 2017
Schedule of Equity Method Investments [Line Items]
Total investments in unconsolidated real estate ventures	$ 360,934			$ 261,791
Advances to unconsolidated real estate ventures	80			20
Total investments in and advances to unconsolidated real estate ventures	361,014			261,811
Canadian Pension Plan Investment Board (CPPIB)
Schedule of Equity Method Investments [Line Items]
Total investments in unconsolidated real estate ventures	136,877			36,317
Landmark
Schedule of Equity Method Investments [Line Items]
Total investments in unconsolidated real estate ventures	86,561			95,368
CBREI Venture
Schedule of Equity Method Investments [Line Items]
Total investments in unconsolidated real estate ventures	$ 75,713			79,062
Berkshire Group [Member]
Schedule of Equity Method Investments [Line Items]
Ownership Interest	50.00%
Total investments in unconsolidated real estate ventures	$ 38,124			27,761
Brandywine
Schedule of Equity Method Investments [Line Items]
Ownership Interest	30.00%
Total investments in unconsolidated real estate ventures	$ 13,858			13,741
CIM/PacLife [Member]
Schedule of Equity Method Investments [Line Items]
Ownership Interest	16.70%		16.67%
Total investments in unconsolidated real estate ventures	$ 9,664			0
JP Morgan
Schedule of Equity Method Investments [Line Items]
Ownership Interest	0.00%	5.00%
Total investments in unconsolidated real estate ventures	$ 0			9,296
Other
Schedule of Equity Method Investments [Line Items]
Total investments in unconsolidated real estate ventures	$ 137			$ 246
Minimum | Canadian Pension Plan Investment Board (CPPIB)
Schedule of Equity Method Investments [Line Items]
Ownership Interest	55.00%
Minimum | Landmark
Schedule of Equity Method Investments [Line Items]
Ownership Interest	1.80%
Minimum | CBREI Venture
Schedule of Equity Method Investments [Line Items]
Ownership Interest	5.00%
Maximum | Canadian Pension Plan Investment Board (CPPIB)
Schedule of Equity Method Investments [Line Items]
Ownership Interest	79.20%
Maximum | Landmark
Schedule of Equity Method Investments [Line Items]
Ownership Interest	49.00%
Maximum | CBREI Venture
Schedule of Equity Method Investments [Line Items]
Ownership Interest	64.00%

Investments in and Advances t_4

Investments in and Advances to Unconsolidated Real Estate Ventures - Narrative (Details) - USD ($)	1 Months Ended			3 Months Ended	9 Months Ended
	Aug. 31, 2018	Feb. 28, 2018	Jan. 31, 2018	Sep. 30, 2018	Sep. 30, 2018	Sep. 30, 2017
Schedule of Equity Method Investments [Line Items]
Deconsolidation of 1900 N Street				$ 95,923,000	$ 95,923,000	$ 0
Return on capital from unconsolidated real estate ventures					6,820,000	1,149,000
Distribution of capital from sale of interest in an unconsolidated real estate venture					$ 24,602,000	$ 0
Equity Method Investment, Realized Gain (Loss) on Disposal				$ 15,500,000
CIM/PacLife [Member]
Schedule of Equity Method Investments [Line Items]
Ownership Interest			16.67%	16.70%	16.70%
Payments to Acquire Interest in Joint Venture			$ 10,100,000
1900 N Street
Schedule of Equity Method Investments [Line Items]
Ownership Interest		100.00%
Equity Method Investment, Ownership Percentage After Funding Of Contributions		55.00%
1101 17th Street [Member]
Schedule of Equity Method Investments [Line Items]
Equity Method Investment, Ownership Percentage After Funding Of Contributions				55.00%	55.00%
Return on capital from unconsolidated real estate ventures				$ 890,000	$ 5,400,000
JP Morgan [Member]
Schedule of Equity Method Investments [Line Items]
Ownership Interest	5.00%			0.00%	0.00%
Distribution of capital from sale of interest in an unconsolidated real estate venture	$ 24,600,000
Equity Method Investment, Realized Gain (Loss) on Disposal					$ 15,500,000
Legacy JBG Funds [Member] | CIM/PacLife [Member]
Schedule of Equity Method Investments [Line Items]
Ownership Interest			47.64%
Canadian Pension Plan Investment Board (CPPIB) | 1900 N Street
Schedule of Equity Method Investments [Line Items]
Ownership Interest		45.00%
Deconsolidation of 1900 N Street		$ 95,900,000
Long-term Purchase Commitment, Amount		$ 101,000,000

Investments in and Advances t_5

Investments in and Advances to Unconsolidated Real Estate Ventures - Summary of Debt (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Equity Method Investments and Joint Ventures [Abstract]
Variable rate, weighted average interest rate	4.96%
Variable rate	$ 536,950	$ 534,500
Fixed rate, weighted average interest rate	3.95%
Fixed rate	$ 852,674	657,701
Unconsolidated real estate ventures - mortgages payable	1,389,624	1,192,201
Unamortized deferred financing costs	(2,555)	(2,000)
Unconsolidated real estate ventures - mortgages payable, net	$ 1,387,069	$ 1,190,201

Investments in and Advances t_6

Investments in and Advances to Unconsolidated Real Estate Ventures - Condensed Combined Financial Information (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017
Combined balance sheet information:
Real estate, net	$ 2,425,633		$ 2,425,633		$ 2,106,670
Other assets, net	307,105		307,105		264,731
Total assets	2,732,738		2,732,738		2,371,401
Mortgages payable, net	1,387,069		1,387,069		1,190,201
Other liabilities, net	100,104		100,104		76,416
Total liabilities	1,487,173		1,487,173		1,266,617
Total equity	1,245,565		1,245,565		1,104,784
Total liabilities and equity	2,732,738		2,732,738		$ 2,371,401
Combined income statement information:
Total revenue	76,247	$ 46,830	236,938	$ 83,387
Operating income	6,861	3,237	23,719	14,576
Net loss	$ (6,970)	$ (5,191)	$ (12,159)	$ (414)

Variable Interest Entities (Det

Variable Interest Entities (Details) $ in Millions	Sep. 30, 2018USD ($)properties	Dec. 31, 2017USD ($)
Variable Interest Entity [Line Items]
Number of Real Estate Properties | properties	65
Variable Interest Entity, Not Primary Beneficiary
Variable Interest Entity [Line Items]
Assets	$ 269.1	$ 163.5
Variable Interest Entity, Primary Beneficiary
Variable Interest Entity [Line Items]
Assets	188.4	111
Liabilities	$ 22.8	$ 8.8
Number of Real Estate Properties	2	2

Other Assets, Net - Summary of

Other Assets, Net - Summary of Other Assets, Net (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Deferred Costs, Capitalized, Prepaid, and Other Assets Disclosure [Abstract]
Deferred leasing costs	$ 189,959	$ 171,153
Accumulated amortization	(72,217)	(67,180)
Deferred leasing costs, net	117,742	103,973
Prepaid expenses	14,623	9,038
Identified intangible assets, net	94,221	126,467
Deferred financing costs on credit facility, net	5,292	6,654
Deposits	3,592	6,317
Derivative Instruments in Hedges, Assets, at Fair Value	28,356	2,141
Other	18,132	9,333
Total other assets, net	$ 281,958	$ 263,923

Debt - Schedule of Mortgages Pa

Debt - Schedule of Mortgages Payable (Details) - Mortgages payable - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Debt Instrument [Line Items]
Variable interest rate	4.16%
Fixed interest rate	4.19%
Variable rate amount	$ 182,996	$ 498,253
Fixed rate amount	1,590,983	1,537,706
Debt, gross	1,773,979	2,035,959
Unamortized deferred financing costs and premium/ discount, net	(4,041)	(10,267)
Debt, net	1,769,938	$ 2,025,692
1233 20th Street [Member]
Debt Instrument [Line Items]
Debt, net	$ 42,000

Debt - Narrative (Details)

Debt - Narrative (Details)	1 Months Ended		3 Months Ended		9 Months Ended		12 Months Ended
	Jul. 31, 2018USD ($)	Jan. 31, 2018USD ($)	Sep. 30, 2018USD ($)extension_option	Sep. 30, 2017USD ($)	Sep. 30, 2018USD ($)extension_option	Sep. 30, 2017USD ($)	Dec. 31, 2017USD ($)
Line of Credit Facility [Line Items]
Borrowings under mortgages payable					$ 43,823,000	$ 242,018,000
Loss on extinguishment of debt			$ (79,000)	$ (689,000)	(4,536,000)	(689,000)
Borrowings under revolving credit facility					35,000,000	$ 115,751,000
Mortgages payable
Line of Credit Facility [Line Items]
Net carrying value of real estate collateralizing the mortgages payable			2,300,000,000		2,300,000,000
Repayment of mortgages payable					251,100,000
Derivative, notional amount			1,300,000,000		1,300,000,000		$ 1,400,000,000
Derivatives Entered Into, Notional Value					381,300,000
Debt, gross			1,773,979,000		1,773,979,000		2,035,959,000
Line of credit
Line of Credit Facility [Line Items]
Credit facility, maximum borrowing capacity			1,400,000,000		1,400,000,000
Line of credit | Revolving credit facility
Line of Credit Facility [Line Items]
Credit facility, maximum borrowing capacity			$ 1,000,000,000		$ 1,000,000,000
Number of debt extension options | extension_option			2		2
Debt extension option period (in months)					6 months
Line of credit | Tranche A-1 Term Loan
Line of Credit Facility [Line Items]
Derivative, notional amount			$ 100,000,000		$ 100,000,000		50,000,000
Credit facility, maximum borrowing capacity			200,000,000		200,000,000
Borrowings under revolving credit facility		$ 50,000,000
Debt, gross			100,000,000		100,000,000		50,000,000
Line of credit | Tranche A-2 Term Loan Credit Facility [Member]
Line of Credit Facility [Line Items]
Credit facility, maximum borrowing capacity			200,000,000		200,000,000
Borrowings under revolving credit facility	$ 200,000,000
Debt, gross			$ 200,000,000		$ 200,000,000		$ 0
Minimum | LIBOR | Line of credit | Tranche A-1 Term Loan
Line of Credit Facility [Line Items]
Basis spread on variable rate					2.12%		1.97%

Debt - Summary of Amounts Outst

Debt - Summary of Amounts Outstanding under the Credit Facility (Details) - USD ($) $ in Thousands	1 Months Ended	9 Months Ended
	May 31, 2018	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017
Line of Credit Facility [Line Items]
Debt Issuance Costs, Line of Credit Arrangements, Net		$ 5,292		$ 6,654
Repayments of Lines of Credit		150,751	$ 0
Revolving credit facility
Line of Credit Facility [Line Items]
Repayments of Lines of Credit	$ 115,000
Tranche A-1 and A-2 Loans [Member]
Line of Credit Facility [Line Items]
Debt, gross		300,000		50,000
Unamortized deferred financing costs, net		(3,019)		(3,463)
Debt, net		$ 296,981		46,537
Line of credit | Revolving credit facility
Line of Credit Facility [Line Items]
Interest Rate (1)		3.36%
Debt, net		$ 0		115,751
Letters of credit		$ 5,700		5,700
Line of credit | Tranche A-1 Term Loan
Line of Credit Facility [Line Items]
Interest Rate (1)		3.32%
Debt, gross		$ 100,000		50,000
Line of credit | Tranche A-2 Term Loan Credit Facility [Member]
Line of Credit Facility [Line Items]
Interest Rate (1)		3.81%
Debt, gross		$ 200,000		$ 0

Other Liabilities, Net - Summar

Other Liabilities, Net - Summary of Other Liabilities (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Schedule of Other Liabilities [Line Items]
Lease intangible liabilities	$ 40,179	$ 44,917
Accumulated amortization	(25,523)	(26,950)
Lease intangible liabilities, net	14,656	17,967
Prepaid rent	15,030	15,751
Lease assumption liabilities and accrued tenant incentives	49,510	50,866
Capital lease obligation	15,736	15,819
Security deposits	13,009	13,618
Ground lease deferred rent payable	3,498	3,730
Net deferred tax liability	6,446	8,202
Dividends payable	0	31,097
Other	1,667	4,227
Total other liabilities, net	$ 119,552	$ 161,277

Redeemable Noncontrolling Int_3

Redeemable Noncontrolling Interests - Narrative (Details) - shares shares in Thousands	Jul. 18, 2017	Sep. 30, 2018	Sep. 30, 2018
Noncontrolling Interest [Line Items]
Common Shares Issued During Period in Connection with Redemption of OP Units		2,962
JBG Smith, LP
Noncontrolling Interest [Line Items]
Ownership interest by parent		87.80%	87.80%
Consolidated Real Estate Venture
Noncontrolling Interest [Line Items]
Ownership interest by parent		85.40%	85.40%
Ownership interest by parent, threshold for capital contributions to cease		97.00%	97.00%
OP Units
Noncontrolling Interest [Line Items]
Common shares and OP Units issued in consideration	19,800		16,800
Common Shares Issued During Period in Connection with Redemption of OP Units		3,000
OP Units | JBG Smith, LP
Noncontrolling Interest [Line Items]
Ownership interest by parent		12.20%	12.20%
Minimum
Noncontrolling Interest [Line Items]
Redemption period			2 years
Maximum
Noncontrolling Interest [Line Items]
Redemption period			7 years

Redeemable Noncontrolling Int_4

Redeemable Noncontrolling Interests - Summary of the Activity of Redeemable Noncontrolling Interests (Details) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Noncontrolling Interest [Line Items]
Corporate and other	$ 12,415,000	$ 10,593,000	$ 37,759,000	$ 35,536,000
Temporary Equity
Beginning Balance			609,129,000	0
Fair value of OP Unit redemptions			(109,208,000)	0
Issuance of common limited partnership units at the Separation			0	96,632,000
OP Units issued in connection with the Combination (1)			0	359,967,000
Net income (loss) attributable to redeemable noncontrolling interests			6,532,000	(2,481,000)
Other comprehensive income			3,406,000	0
Contributions (distributions)			(8,263,000)	0
Share-based compensation expense			39,376,000	15,799,000
Adjustment to redemption value			21,346,000	97,084,000
Ending Balance	562,318,000	567,001,000	562,318,000	567,001,000
Business Combination, Contingent Consideration, Liability		110,600,000		110,600,000
JBG Smith, LP
Temporary Equity
Beginning Balance			603,717,000	0
Fair value of OP Unit redemptions			(109,208,000)	0
Issuance of common limited partnership units at the Separation			0	96,632,000
OP Units issued in connection with the Combination (1)			0	359,967,000
Net income (loss) attributable to redeemable noncontrolling interests			6,537,000	(2,481,000)
Other comprehensive income			3,406,000	0
Contributions (distributions)			(8,763,000)	0
Share-based compensation expense			39,376,000	15,799,000
Adjustment to redemption value			21,346,000	97,084,000
Ending Balance	556,411,000	567,001,000	556,411,000	567,001,000
Consolidated Real Estate Venture
Temporary Equity
Beginning Balance			5,412,000	0
Fair value of OP Unit redemptions			0	0
Issuance of common limited partnership units at the Separation			0	0
OP Units issued in connection with the Combination (1)			0	0
Net income (loss) attributable to redeemable noncontrolling interests			(5,000)	0
Other comprehensive income			0	0
Contributions (distributions)			500,000	0
Share-based compensation expense			0	0
Adjustment to redemption value			0	0
Ending Balance	5,907,000	0	5,907,000	0
Legacy JBG Funds [Member] | Affiliated Entity [Member]
Noncontrolling Interest [Line Items]
Corporate and other	$ 1,200,000	$ 792,000	$ 3,600,000	$ 792,000

Share-Based Payments - Time-Bas

Share-Based Payments - Time-Based LTIP Units (Details) $ / shares in Units, $ in Millions	1 Months Ended	9 Months Ended
	Feb. 28, 2018USD ($)installment$ / sharesshares	Sep. 30, 2018
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Additional Disclosures [Abstract]
Compensation expense recognition period (in years)		2 years 7 months
Time-Based LTIP Units
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Additional Disclosures [Abstract]
Equity grants (in shares) | shares	357,759
Fair value of awards on grant date | $	$ 11.2
Number of installments | installment	4
Compensation expense recognition period (in years)	4 years
Weighted Average Grant-Date Fair Value
Granted (in dollars per share) | $ / shares	$ 31.38
Measurement Input, Price Volatility [Member] | Time-Based LTIP Units
Weighted Average Grant-Date Fair Value
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Expected Volatility Rate	20.00%
Measurement Input, Risk Free Interest Rate [Member] | Time-Based LTIP Units
Weighted Average Grant-Date Fair Value
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Risk Free Interest Rate	2.10%
Measurement Input, Expected Term [Member] | Time-Based LTIP Units
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Additional Disclosures [Abstract]
Expected life (in years)	2 years

Share-Based Payments - Performa

Share-Based Payments - Performance-Based LTIP Units (Details) - USD ($) $ / shares in Units, $ in Millions	1 Months Ended	9 Months Ended
	Feb. 28, 2018	Sep. 30, 2018
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Compensation expense recognition period (in years)		2 years 7 months
Performance-Based LTIP Units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Equity grants (in shares)	553,489
Vesting period	3 years
Fair value of awards on grant date	$ 9.4
Fair value of awards on grant date (in dollars per unit)	$ 17.04
Compensation expense recognition period (in years)	4 years
Performance-Based LTIP Units | Vesting Period One
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Percentage of vesting rights for each tranche	50.00%
Performance-Based LTIP Units | Vesting Period Two
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Percentage of vesting rights for each tranche	50.00%
Measurement Input, Expected Dividend Rate [Member] | Performance-Based LTIP Units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Dividend yield rate	2.70%
Measurement Input, Price Volatility [Member] | Performance-Based LTIP Units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Expected Volatility Rate	19.90%
Measurement Input, Risk Free Interest Rate [Member] | Performance-Based LTIP Units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Risk Free Interest Rate	2.30%

Share-Based Payments - LTIPs (D

Share-Based Payments - LTIPs (Details) - LTIP Units [Member]	1 Months Ended
	May 31, 2018USD ($)shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period | shares	25,770
Deferred Compensation Arrangement with Individual, Fair Value of Shares Issued | $	$ 794,000

Share-Based Payments - Summary

Share-Based Payments - Summary of Share-Based Compensation Expense (Details) - USD ($) $ in Thousands	1 Months Ended	3 Months Ended		9 Months Ended
	Feb. 28, 2018	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation related to Formation Transaction		$ 8,387	$ 14,445	$ 26,912	$ 14,445
Allocated Share-based Compensation Expense, Before Capitalization		13,287	16,031	42,069	17,325
Less amount capitalized		(873)	(161)	(2,379)	(161)
Share-based compensation expense		12,414	15,870	39,690	17,164
Total unrecognized compensation expense		107,200		$ 107,200
Compensation expense recognition period (in years)				2 years 7 months
Time-Based LTIP Units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation related to Formation Transaction		2,520	885	$ 7,772	885
Compensation expense recognition period (in years)	4 years
Performance-Based LTIP Units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation related to Formation Transaction		1,391	469	3,898	469
Compensation expense recognition period (in years)	4 years
LTIP Units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation related to Formation Transaction		0	0	794	0
Other Equity Awards
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation related to Formation Transaction		989	232	2,693	1,526
Share-based compensation expense - other
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation related to Formation Transaction		4,900	1,586	15,157	2,880
Formation Awards
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation related to Formation Transaction		1,375	3,963	4,192	3,963
LTIP and OP Units (1)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation related to Formation Transaction		7,012	10,482	22,720	10,482
Share-based compensation related to Formation Transaction
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation related to Formation Transaction		$ 8,387	$ 14,445	$ 26,912	$ 14,445

Interest Expense Interest Exp_2

Interest Expense Interest Expense (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Interest expense	$ 23,465	$ 16,378	$ 69,024	$ 45,011
Amortization of deferred financing costs	1,043	739	3,501	1,527
Unrealized Gain (Loss) on Derivatives	(287)	467	1,264	467
Derivative, Gain (Loss) on Derivative, Net	(135)	27	(135)	27
Capitalized interest	(5,681)	(1,368)	(14,863)	(2,285)
Interest Expense	$ 18,979	$ 15,309	$ 56,263	$ 43,813

Earnings (Loss) Per Common Sh_3

Earnings (Loss) Per Common Share - Schedule of Earnings (Loss) Per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Earnings Per Share [Abstract]
Net income (loss)	$ 26,382	$ (77,991)	$ 45,619	$ (60,332)
Net (income) loss attributable to redeemable noncontrolling interests	3,552	(8,160)	6,532	(2,481)
Net loss attributable to noncontrolling interests	0	0	127	0
Net income (loss) attributable to common shareholders	22,830	(69,831)	39,214	(57,851)
Distributions to participating securities	(153)	0	(527)	0
Net income (loss) available to common shareholders — basic and diluted	$ 22,677	$ (69,831)	$ 38,687	$ (57,851)
Weighted average number of common shares outstanding — basic and diluted (1)	119,835	114,744	118,588	105,347
Earnings (loss) per common share:
Basic (in dollars per share)	$ 0.19	$ (0.61)	$ 0.33	$ (0.55)
Diluted (in dollars per share)	$ 0.19	$ (0.61)	$ 0.33	$ (0.55)

Earnings (Loss) Per Common Sh_4

Earnings (Loss) Per Common Share - Narrative (Details) - shares	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share (in shares)	3,900,000	2,600,000	3,800,000	900,000

Earnings (Loss) Per Common Sh_5

Earnings (Loss) Per Common Share - Antidilutive Securities Excluded (Details) - shares	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share (in shares)	3,900,000	2,600,000	3,800,000	900,000

Fair Value Measurements - Narra

Fair Value Measurements - Narrative (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Fair Value Disclosures [Abstract]
Net unrealized gain on derivative designated as cash flow hedge			$ 27,800
Gain expected to be reclassified into interest expense within the next 12 months			4,600
Unrealized Gain (Loss) on Derivatives	$ (287)	$ 467	$ 1,264	$ 467

Fair Value Measurements - Sched

Fair Value Measurements - Schedule of Fair Value, Assets and Liabilities Measured on Recurring Basis (Details) - Interest rate swap and caps - Recurring - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Other Assets, Net | Designated as Hedging Instrument
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Classified as assets in Other assets, net	$ 21,119	$ 1,506
Other Assets, Net | Designated as Hedging Instrument | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Classified as assets in Other assets, net	0	0
Other Assets, Net | Designated as Hedging Instrument | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Classified as assets in Other assets, net	21,119	1,506
Other Assets, Net | Designated as Hedging Instrument | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Classified as assets in Other assets, net	0	0
Other Assets, Net | Not Designated as Hedging Instrument
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Classified as assets in Other assets, net	7,237	635
Other Assets, Net | Not Designated as Hedging Instrument | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Classified as assets in Other assets, net	0	0
Other Assets, Net | Not Designated as Hedging Instrument | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Classified as assets in Other assets, net	7,237	635
Other Assets, Net | Not Designated as Hedging Instrument | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Classified as assets in Other assets, net	0	0
Other Liabilities, Net | Designated as Hedging Instrument
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Classified as liabilities in Other liabilities, net	954	2,640
Other Liabilities, Net | Designated as Hedging Instrument | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Classified as liabilities in Other liabilities, net	0	0
Other Liabilities, Net | Designated as Hedging Instrument | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Classified as liabilities in Other liabilities, net	954	2,640
Other Liabilities, Net | Designated as Hedging Instrument | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Classified as liabilities in Other liabilities, net	$ 0	0
Other Liabilities, Net | Not Designated as Hedging Instrument
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Classified as liabilities in Other liabilities, net		22
Other Liabilities, Net | Not Designated as Hedging Instrument | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Classified as liabilities in Other liabilities, net		0
Other Liabilities, Net | Not Designated as Hedging Instrument | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Classified as liabilities in Other liabilities, net		22
Other Liabilities, Net | Not Designated as Hedging Instrument | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Classified as liabilities in Other liabilities, net		$ 0

Fair Value Measurements - Finan

Fair Value Measurements - Financial Assets and Liabilities Not Measured at Fair Value (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Mortgages payable | Carrying Amount
Financial liabilities:
Financial liabilities	$ 1,773,979	$ 2,035,959
Mortgages payable | Fair Value
Financial liabilities:
Financial liabilities	1,785,978	2,060,899
Revolving credit facility | Carrying Amount
Financial liabilities:
Financial liabilities	0	115,751
Revolving credit facility | Fair Value
Financial liabilities:
Financial liabilities	0	115,768
Unsecured term loans | Carrying Amount
Financial liabilities:
Financial liabilities	300,000	50,000
Unsecured term loans | Fair Value
Financial liabilities:
Financial liabilities	$ 300,307	$ 50,029

Segment Information - Narrative

Segment Information - Narrative (Details) $ in Thousands	9 Months Ended
	Sep. 30, 2018USD ($)segment	Sep. 30, 2017segment	Dec. 31, 2017USD ($)
Segment Reporting Information [Line Items]
Number of reportable segments | segment	3
Number of operating segments | segment		3
Other assets, net | $	$ 281,958		$ 263,923
Third-Party Real Estate Services Segment
Segment Reporting Information [Line Items]
Other assets, net | $	$ 40,400		$ 45,700

Segment Information - Schedule

Segment Information - Schedule of Reconciliation of Net Income Attributable to Parent (Details) - USD ($)	3 Months Ended			9 Months Ended
	Sep. 30, 2018	Dec. 31, 2017	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Business Acquisition [Line Items]
Net income (loss) attributable to common shareholders	$ 22,830,000		$ (69,831,000)	$ 39,214,000	$ (57,851,000)
Depreciation and amortization	46,603,000		43,951,000	143,880,000	109,726,000
Corporate and other	12,415,000		10,593,000	37,759,000	35,536,000
Third-party real estate services	20,754,000		21,178,000	64,552,000	30,362,000
Share-based compensation related to Formation Transaction	8,387,000		14,445,000	26,912,000	14,445,000
Transaction and other costs	4,126,000		104,095,000	12,134,000	115,173,000
Interest expense	18,979,000		15,309,000	56,263,000	43,813,000
Loss on extinguishment of debt	79,000		689,000	4,536,000	689,000
Reduction of gain (gain) on bargain purchase	0	$ (3,400,000)	(27,771,000)	7,606,000	(27,771,000)
Income tax benefit	(841,000)		(1,034,000)	(1,436,000)	(317,000)
Net (income) loss attributable to redeemable noncontrolling interests	3,552,000		(8,160,000)	6,532,000	(2,481,000)
Third-party real estate services, including reimbursements	23,788,000		25,141,000	72,278,000	38,881,000
Other income	1,708,000		1,158,000	4,904,000	3,701,000
Income (loss) from unconsolidated real estate ventures, net	13,484,000		(1,679,000)	15,418,000	(1,365,000)
Interest and other income (loss), net	4,091,000		(379,000)	5,177,000	1,366,000
Gains (Losses) on Sales of Investment Real Estate	11,938,000		0	45,789,000	0
Net loss attributable to noncontrolling interests	0		0	(127,000)	0
Consolidated NOI	81,875,000		79,223,000	$ 254,259,000	218,741,000
JBG Companies [Member]
Business Acquisition [Line Items]
Transaction and other costs	$ 4,126,000		$ 104,095,000		$ 115,200,000

Segment Information - Summary o

Segment Information - Summary of NOI by Segment (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Segment Reporting Information [Line Items]
Property rentals	$ 123,203	$ 116,458	$ 375,094	$ 316,899
Reimbursements from Tenants	9,744	9,593	28,651	27,161
Total rental revenue	132,947	126,051	403,745	344,060
Property operating	34,167	29,634	95,462	77,341
Real estate taxes	16,905	17,194	54,024	47,978
Total rental expense	51,072	46,828	149,486	125,319
Consolidated NOI	81,875	79,223	254,259	218,741
Operating Segments | Office
Segment Reporting Information [Line Items]
Property rentals	95,438	91,534	294,238	249,532
Reimbursements from Tenants	8,036	7,917	23,480	22,738
Total rental revenue	103,474	99,451	317,718	272,270
Property operating	29,086	27,000	83,666	71,377
Real estate taxes	12,463	13,038	39,429	37,185
Total rental expense	41,549	40,038	123,095	108,562
Consolidated NOI	61,925	59,413	194,623	163,708
Operating Segments | Multifamily
Segment Reporting Information [Line Items]
Property rentals	26,167	23,397	75,644	62,050
Reimbursements from Tenants	1,563	1,548	4,778	3,772
Total rental revenue	27,730	24,945	80,422	65,822
Property operating	8,144	6,796	22,844	16,716
Real estate taxes	3,506	2,952	10,561	7,973
Total rental expense	11,650	9,748	33,405	24,689
Consolidated NOI	16,080	15,197	47,017	41,133
Operating Segments | Other
Segment Reporting Information [Line Items]
Property rentals	1,956	4,171	6,068	9,623
Reimbursements from Tenants	145	128	393	651
Total rental revenue	2,101	4,299	6,461	10,274
Property operating	2,673	3,502	5,416	11,330
Real estate taxes	936	1,204	4,034	2,820
Total rental expense	3,609	4,706	9,450	14,150
Consolidated NOI	(1,508)	(407)	(2,989)	(3,876)
Elimination of Intersegment Activity
Segment Reporting Information [Line Items]
Property rentals	(358)	(2,644)	(856)	(4,306)
Reimbursements from Tenants	0	0	0	0
Total rental revenue	(358)	(2,644)	(856)	(4,306)
Property operating	(5,736)	(7,664)	(16,464)	(22,082)
Real estate taxes	0	0	0	0
Total rental expense	(5,736)	(7,664)	(16,464)	(22,082)
Consolidated NOI	$ 5,378	$ 5,020	$ 15,608	$ 17,776

Segment Information - Summary_2

Segment Information - Summary of Certain Balance Sheet Data by Segment (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Segment Reporting Information [Line Items]
Assets Held-for-sale, Not Part of Disposal Group	$ 137,455	$ 8,293
Real estate, at cost	5,693,545	6,017,504
Investments in and advances to unconsolidated real estate ventures	361,014	261,811
Total assets (1)	6,011,194	6,071,807
Operating Segments | Office
Segment Reporting Information [Line Items]
Assets Held-for-sale, Not Part of Disposal Group	130,800	1,700
Real estate, at cost	3,420,068	3,953,314
Investments in and advances to unconsolidated real estate ventures	211,301	124,659
Total assets (1)	3,488,847	3,542,977
Operating Segments | Multifamily
Segment Reporting Information [Line Items]
Assets Held-for-sale, Not Part of Disposal Group	2,200
Real estate, at cost	1,599,912	1,476,423
Investments in and advances to unconsolidated real estate ventures	105,028	98,835
Total assets (1)	1,475,233	1,434,999
Operating Segments | Other
Segment Reporting Information [Line Items]
Assets Held-for-sale, Not Part of Disposal Group	4,500	6,600
Real estate, at cost	673,565	587,767
Investments in and advances to unconsolidated real estate ventures	44,685	38,317
Total assets (1)	1,211,537	1,299,085
Elimination of Intersegment Activity
Segment Reporting Information [Line Items]
Real estate, at cost	0	0
Investments in and advances to unconsolidated real estate ventures	0	0
Total assets (1)	$ (164,423)	$ (205,254)

Commitments and Contingencies -

Commitments and Contingencies - Narrative (Details)	9 Months Ended
	Sep. 30, 2018USD ($)
Real Estate Properties [Line Items]
General liability insurance limit	$ 200,000,000
Property and rental value insurance coverage limit	2,000,000,000
Terrorist acts insurance coverage limit	2,000,000,000
Purchase obligation	396,200,000
Additional capital funding committed amount	48,600,000
Consolidated Properties
Real Estate Properties [Line Items]
Purchase obligation	310,800,000
Principal payment guarantees	69,600,000
Unconsolidated Properties
Real Estate Properties [Line Items]
Purchase obligation	85,400,000
Principal payment guarantees	$ 0
Minimum
Real Estate Properties [Line Items]
Commitment amortization period	2 years
Minimum | Unconsolidated Properties
Real Estate Properties [Line Items]
Commitment amortization period	2 years
Maximum
Real Estate Properties [Line Items]
Commitment amortization period	3 years
Maximum | Unconsolidated Properties
Real Estate Properties [Line Items]
Commitment amortization period	3 years

Transactions with Vornado and_2

Transactions with Vornado and Related Parties (Details)	Jul. 18, 2017USD ($)	Jul. 17, 2017USD ($)	Aug. 12, 2014USD ($)	Jun. 30, 2016USD ($)ft²	Sep. 30, 2018USD ($)	Sep. 30, 2017USD ($)	Sep. 30, 2018USD ($)	Sep. 30, 2017USD ($)	Dec. 31, 2017USD ($)	Aug. 31, 2014USD ($)ft²
Related Party Transaction [Line Items]
Proceeds from credit facility							$ 35,000,000	$ 115,751,000
Third-party real estate services, including reimbursements					$ 23,788,000	$ 25,141,000	72,278,000	38,881,000
Corporate and other					12,415,000	10,593,000	37,759,000	35,536,000
Universal Buildings, Washington DC
Related Party Transaction [Line Items]
Area of real estate property (in square feet) | ft²										687,000
Bowen Building, Washington DC [Member]
Related Party Transaction [Line Items]
Area of real estate property (in square feet) | ft²				231,000
Financing of the Universal Buildings
Related Party Transaction [Line Items]
Debt instrument, face amount										$ 185,000,000
Affiliated Entity [Member] | Vornado | Vornado's revolving credit facility
Related Party Transaction [Line Items]
Interest expense to Vornado						120,000		1,300,000
Proceeds from credit facility				$ 115,600,000
Affiliated Entity [Member] | Vornado | Mortgage loan secured by Bowen Building
Related Party Transaction [Line Items]
Repayment of mortgages payable				115,000,000
Accrued interest on mortgage loan				$ 608,000
Affiliated Entity [Member] | Legacy JBG Funds [Member]
Related Party Transaction [Line Items]
Corporate and other					1,200,000	792,000	3,600,000	792,000
Affiliated Entity [Member] | Allocations of centralized corporate costs | Vornado
Related Party Transaction [Line Items]
Allocated amounts included in general and administrative expense						873,000		13,000,000
Affiliated Entity [Member] | Financing transactions | Vornado | Financing of the Universal Buildings
Related Party Transaction [Line Items]
Loan to Vornado			$ 86,000,000
Interest Income on loan receivable from Vornado						130,000		1,800,000
Affiliated Entity [Member] | Financing transactions | Vornado | Financing of the Universal Buildings | LIBOR
Related Party Transaction [Line Items]
Mortgage loan interest rate			2.90%
Affiliated Entity [Member] | Financing transactions | Vornado | Note agreement for development of Bartlett
Related Party Transaction [Line Items]
Debt instrument, face amount	$ 170,000,000
Interest expense to Vornado						365,000		4,100,000
Affiliated Entity [Member] | Supervise cleaning, engineering and security services | BMS
Related Party Transaction [Line Items]
Related party transaction amount					5,400,000	3,600,000	15,500,000	9,900,000
Affiliated Entity [Member] | Separation and Combination transaction | Vornado
Related Party Transaction [Line Items]
Expenses from related parties					931,000	912,000	3,200,000	912,000
Revenue from related parties					507,000	$ 68,000	1,600,000	$ 68,000
Transaction services, initial period (in months)	2 years
Affiliated Entity [Member] | Fees from Legacy JBG Funds | Legacy JBG Funds [Member]
Related Party Transaction [Line Items]
Third-party real estate services, including reimbursements					8,700,000		25,600,000
Accounts Receivable, Related Parties					$ 3,100,000		3,100,000		$ 3,100,000
Trustee | Consulting agreement
Related Party Transaction [Line Items]
Transaction services, initial period (in months)		24 months
Related party transaction, monthly amount		$ 169,400
JBG Companies [Member]
Related Party Transaction [Line Items]
Liability incurred in connection with the Combination	$ 4,100,000						$ 1,400,000

Subsequent Events (Details)

Subsequent Events (Details) - $ / shares	Nov. 06, 2018	Sep. 30, 2018
Subsequent Event [Line Items]
Common Stock, Dividends, Per Share, Declared		$ 0.45
Subsequent Event [Member]
Subsequent Event [Line Items]
Common Stock, Dividends, Per Share, Declared	$ 0.225

Uncategorized Items - jbgs-2018

Label	Element	Value
Noncontrolling Interest, Contributions	jbgs_NoncontrollingInterestContributions	$ 250,000
Interest Payable	us-gaap_InterestPayableCurrentAndNoncurrent	0
Interest Payable	us-gaap_InterestPayableCurrentAndNoncurrent	3,216,000
Noncontrolling Interest [Member]
Noncontrolling Interest, Contributions	jbgs_NoncontrollingInterestContributions	$ 250,000