Real Estate - Dispositions (Details) ft² in Thousands, $ in Thousands	1 Months Ended	12 Months Ended
	Feb. 28, 2019 USD ($) a	Dec. 31, 2021 USD ($) ft² property	Dec. 31, 2020 USD ($) ft² property	Dec. 31, 2019 USD ($)	Jul. 31, 2021 USD ($) a
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of properties sold | property		3	2
Disposal Group, Disposed of by Sale, Not Discontinued Operations
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Gain/(Loss) on Sale, net		$ 90,200	$ 90,300	$ 459
Disposal Group, Disposed of by Sale, Not Discontinued Operations | 816 Congress [Member] | Austin, TX
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Area of property | ft²		435
Sales Price		$ 174,000
Gain/(Loss) on Sale, net		$ 77,400
Disposal Group, Disposed of by Sale, Not Discontinued Operations | One South at the Plaza | Charlotte, NC
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Area of property | ft²		891
Sales Price		$ 271,500
Gain/(Loss) on Sale, net		$ 12,700
Disposal Group, Disposed of by Sale, Not Discontinued Operations | Burnett Plaza [Member] | Fort Worth, Texas [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Area of property | ft²		1,000
Sales Price		$ 137,500
Gain/(Loss) on Sale, net		$ (19)
Disposal Group, Disposed of by Sale, Not Discontinued Operations | Hearst Tower | Charlotte, NC
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Area of property | ft²			966
Sales Price			$ 455,500
Gain/(Loss) on Sale, net			$ 90,300
Disposal Group, Disposed of by Sale, Not Discontinued Operations | Woodcrest | Cherry Hill, NJ
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Area of property | ft²			386
Sales Price			$ 25,300
Gain/(Loss) on Sale, net			$ 0
Disposal Group, Disposed of by Sale, Not Discontinued Operations | 100 Mill - Adjacent Land [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Area of property | a					0.7
Sales Price					$ 6,400
Disposal Group, Disposed of by Sale, Not Discontinued Operations | Downtown Atlanta
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Area of property | a	8
Sales Price	$ 13,300
Gain/(Loss) on Sale, net	$ 13,100