Property Acquisitions - 2020 Acquisitions (Details) $ in Millions	1 Months Ended
	Jan. 31, 2020 USD ($) ft²	Dec. 31, 2020 ft²	Oct. 31, 2020 USD ($) ft²
Business Acquisition [Line Items]
Approximate Square Feet		29,500,737
762 Madison Avenue
Business Acquisition [Line Items]
Approximate Square Feet	6,109
Gross Asset Valuation (in millions) | $	$ 29.3
Interest acquired	10.00%
707 Eleventh Avenue
Business Acquisition [Line Items]
Approximate Square Feet	159,720
Gross Asset Valuation (in millions) | $	$ 90.0
15 Beekman
Business Acquisition [Line Items]
Approximate Square Feet	98,412
Gross Asset Valuation (in millions) | $	$ 0.0
590 Fifth Avenue
Business Acquisition [Line Items]
Approximate Square Feet			103,300
Gross Asset Valuation (in millions) | $			$ 107.2
126-132 Nassau Street [Member]
Business Acquisition [Line Items]
Ground leases, term of contract	99 years