The Combination - Fair Value of Definite-lived Assets and Liabilities (Details) - JBG Companies - USD ($) $ in Thousands		9 Months Ended
	Jul. 18, 2017	Sep. 30, 2017
Finite-Lived Intangible Assets [Line Items]
Building and improvements	$ 559,042
Tenant improvements	64,847
Total building and improvements	623,889
Leasehold improvements	4,422
Identified intangible assets	$ 146,600
Weighted average amortization period (in years)	10 years 2 months
Below-market real estate leases	$ 8,449
In-place leases
Finite-Lived Intangible Assets [Line Items]
Identified intangible assets	$ 59,351
Weighted average amortization period (in years)	6 years 5 months
Above-market real estate leases
Finite-Lived Intangible Assets [Line Items]
Identified intangible assets	$ 11,700
Weighted average amortization period (in years)	6 years 3 months
Below-market ground leases
Finite-Lived Intangible Assets [Line Items]
Identified intangible assets	$ 659
Weighted average amortization period (in years)	88 years 6 months
Option to enter into ground lease
Finite-Lived Intangible Assets [Line Items]
Identified intangible assets	$ 17,090
Management and leasing contracts
Finite-Lived Intangible Assets [Line Items]
Identified intangible assets	$ 57,800
Weighted average amortization period (in years)	7 years 5 months
Minimum | Building and improvements
Finite-Lived Intangible Assets [Line Items]
Useful life (in years)		3 years
Minimum | Management and leasing contracts
Finite-Lived Intangible Assets [Line Items]
Useful life (in years)		3 years
Maximum | Building and improvements
Finite-Lived Intangible Assets [Line Items]
Useful life (in years)		40 years
Maximum | Management and leasing contracts
Finite-Lived Intangible Assets [Line Items]
Useful life (in years)		8 years