Subsequent Events - Separation and Combination Narrative (Details) - Subsequent Event $ / shares in Units, shares in Millions, $ in Millions	Jul. 18, 2017 USD ($) ft² building_unit properties person $ / shares shares	Jul. 07, 2017	Jul. 17, 2017 shares
Subsequent Event [Line Items]
Common stock issued (in shares) | shares			94.7
Common limited partnership units (in shares) | shares			5.8
Number of real estate properties | properties	68
Asset under Construction
Subsequent Event [Line Items]
Number of real estate properties | properties	11
Near-Term Development
Subsequent Event [Line Items]
Number of real estate properties | properties	2
Future Development
Subsequent Event [Line Items]
Number of real estate properties | properties	44
Area of real estate property acquired (in square feet)	22,000,000
Wholly Owned Properties | Future Development
Subsequent Event [Line Items]
Area of real estate property acquired (in square feet)	18,300,000
Office Building
Subsequent Event [Line Items]
Number of real estate properties | properties	50
Area of real estate property acquired (in square feet)	13,900,000
Office Building | Asset under Construction
Subsequent Event [Line Items]
Number of real estate properties | properties	5
Area of real estate property acquired (in square feet)	1,300,000
Office Building | Wholly Owned Properties
Subsequent Event [Line Items]
Area of real estate property acquired (in square feet)	11,900,000
Office Building | Wholly Owned Properties | Asset under Construction
Subsequent Event [Line Items]
Area of real estate property acquired (in square feet)	1,200,000
Multifamily
Subsequent Event [Line Items]
Number of real estate properties | properties	14
Number of building units | building_unit	6,016
Multifamily | Asset under Construction
Subsequent Event [Line Items]
Number of real estate properties | properties	6
Number of building units | building_unit	1,334
Multifamily | Near-Term Development
Subsequent Event [Line Items]
Number of real estate properties | properties	1
Number of building units | building_unit	433
Multifamily | Wholly Owned Properties
Subsequent Event [Line Items]
Number of building units | building_unit	4,232
Multifamily | Wholly Owned Properties | Asset under Construction
Subsequent Event [Line Items]
Number of building units | building_unit	1,146
Multifamily | Wholly Owned Properties | Near-Term Development
Subsequent Event [Line Items]
Number of building units | building_unit	303
Other Property
Subsequent Event [Line Items]
Number of real estate properties | properties	4
Area of real estate property acquired (in square feet)	765,000
Other Property | Near-Term Development
Subsequent Event [Line Items]
Number of real estate properties | properties	1
Area of real estate property acquired (in square feet)	65,000
Other Property | Wholly Owned Properties
Subsequent Event [Line Items]
Area of real estate property acquired (in square feet)	348,000
Other Property | Wholly Owned Properties | Near-Term Development
Subsequent Event [Line Items]
Area of real estate property acquired (in square feet)	6,500
JBG Companies
Subsequent Event [Line Items]
Mortgages payable liabilities assumed in acquisition | $	$ 770.0
Equity interest issued for acquisition (in shares) | shares	37.2
Price per share of stock issued for acquisition (in dollars per share) | $ / shares	$ 37.10
Number of real estate properties | properties	30
Number of unrelated owners | person	20
Number of owners turned employees | person	19
Number of owners turned board of trustee members | person	3
JBG Companies | Asset under Construction
Subsequent Event [Line Items]
Number of real estate properties | properties	11
Area of real estate property acquired (in square feet)	2,500,000
JBG Companies | Near-Term Development
Subsequent Event [Line Items]
Number of real estate properties | properties	2
Area of real estate property acquired (in square feet)	401,000
JBG Companies | Future Development
Subsequent Event [Line Items]
Number of real estate properties | properties	26
Area of real estate property acquired (in square feet)	11,700,000
JBG Companies | Wholly Owned Properties | Asset under Construction
Subsequent Event [Line Items]
Area of real estate property acquired (in square feet)	2,200,000
JBG Companies | Wholly Owned Properties | Near-Term Development
Subsequent Event [Line Items]
Area of real estate property acquired (in square feet)	242,000
JBG Companies | Wholly Owned Properties | Future Development
Subsequent Event [Line Items]
Area of real estate property acquired (in square feet)	8,500,000
JBG Companies | Office Building
Subsequent Event [Line Items]
Number of real estate properties | properties	19
Area of real estate property acquired (in square feet)	3,600,000
JBG Companies | Office Building | Wholly Owned Properties
Subsequent Event [Line Items]
Area of real estate property acquired (in square feet)	2,300,000
JBG Companies | Multifamily
Subsequent Event [Line Items]
Number of real estate properties | properties	9
Number of building units | building_unit	2,883
JBG Companies | Multifamily | Wholly Owned Properties
Subsequent Event [Line Items]
Number of building units | building_unit	1,099
JBG Companies | Other Property
Subsequent Event [Line Items]
Number of real estate properties | properties	2
Area of real estate property acquired (in square feet)	490,000
JBG Companies | Other Property | Wholly Owned Properties
Subsequent Event [Line Items]
Area of real estate property acquired (in square feet)	73,000
Affiliate | Vornado
Subsequent Event [Line Items]
Spinoff ratio		0.5
Limited Partners spinoff ratio		0.5
Affiliate | Vornado | Separation and Combination transaction
Subsequent Event [Line Items]
Transaction services, initial period	2 years