220 Central Park South 220 CPS - Narrative (Details) ft² in Thousands, $ in Thousands	3 Months Ended		6 Months Ended		21 Months Ended
	Jun. 30, 2020 USD ($) ft² unit	Jun. 30, 2019 USD ($)	Jun. 30, 2020 USD ($) ft² unit	Jun. 30, 2019 USD ($)	Jun. 30, 2020 USD ($) ft² unit
Real Estate [Line Items]
Net gain on sale of real estate			$ 0	$ 2,571,099
Income tax expense	$ 1,837	$ 26,914	$ 14,650	$ 56,657
220 Central Park South
Real Estate [Line Items]
Square footage of real estate property (in sqft) | ft²	397		397		397
Development costs	$ 1,450,000		$ 1,450,000		$ 1,450,000
Development costs expended	$ 1,419,000		$ 1,419,000		$ 1,419,000
Number of condominium units sold (unit) | unit	4		11		76
Cash proceeds from the sale of real estate	$ 156,972		$ 348,188		$ 2,168,320
Net gain on sale of real estate	55,695		124,284		$ 809,901
Income tax expense	$ 6,690		$ 15,368