Dispositions (Details) $ in Thousands		3 Months Ended		9 Months Ended
	Sep. 09, 2020 USD ($)	Sep. 30, 2020 USD ($) ft²	Sep. 30, 2019 USD ($)	Sep. 30, 2020 USD ($) ft²	Sep. 30, 2019 USD ($)
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Rentable Square Feet | ft²		1,583,121		1,583,121
Gain on sale of real estate		$ 13,669	$ 895	$ 13,669	$ 5,705
Sales-type Lease, Selling Profit (Loss)	$ 3,800			$ 3,822	$ 0
Dispositions
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Rentable Square Feet | ft²		248,016		248,016
Contractual Sales Price		$ 44,200		$ 44,200
Gain on sale of real estate				$ 13,669
3927 Oceanic Drive | Dispositions
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Date of Disposition				Aug. 13, 2020
Rentable Square Feet | ft²		54,740		54,740
Contractual Sales Price		$ 10,300		$ 10,300
Gain on sale of real estate				$ 2,926
121 West 33rd Street | Dispositions
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Date of Disposition				Sep. 18, 2020
Rentable Square Feet | ft²		76,701		76,701
Contractual Sales Price		$ 13,500		$ 13,500
Gain on sale of real estate				$ 7,475
2700-2722 South Fairview Street | Dispositions
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Date of Disposition				Sep. 30, 2020
Rentable Square Feet | ft²		116,575		116,575
Contractual Sales Price		$ 20,400		$ 20,400
Gain on sale of real estate	3,300			$ 3,268
Sale of real estate, transaction costs	$ (600)