Organization and Basis of Presentation - Narrative (Details)	Mar. 31, 2020 ft² property building
Real Estate Properties [Line Items]
Number of Real Estate Properties	64
Asset under Construction
Real Estate Properties [Line Items]
Number of Real Estate Properties	4
Future Development
Real Estate Properties [Line Items]
Number of Real Estate Properties	37
Area of real estate property (in square feet) | ft²	20,000,000.0
Commercial Real Estate [Member]
Real Estate Properties [Line Items]
Number of Real Estate Properties	44
Area of real estate property (in square feet) | ft²	13,300,000
Multifamily
Real Estate Properties [Line Items]
Number of Real Estate Properties	20
Number of Units in Real Estate Property | building	7,367
Multifamily | Asset under Construction
Real Estate Properties [Line Items]
Number of Real Estate Properties	2
Number of Units in Real Estate Property | building	755
Wholly Owned Properties | Commercial Real Estate [Member] | Asset under Construction
Real Estate Properties [Line Items]
Number of Real Estate Properties	2
Area of real estate property (in square feet) | ft²	380,000
Partially Owned Properties | Future Development
Real Estate Properties [Line Items]
Area of real estate property (in square feet) | ft²	16,700,000
Partially Owned Properties | Commercial Real Estate [Member]
Real Estate Properties [Line Items]
Area of real estate property (in square feet) | ft²	11,100,000
Partially Owned Properties | Multifamily
Real Estate Properties [Line Items]
Number of Units in Real Estate Property | building	5,583
Partially Owned Properties | Multifamily | Asset under Construction
Real Estate Properties [Line Items]
Number of Units in Real Estate Property | ft²	577
JBG Smith, LP
Real Estate Properties [Line Items]
Ownership interest by parent	90.30%