220 Central Park South 220 CPS (Narrative) (Details) ft² in Thousands, $ in Thousands	3 Months Ended		9 Months Ended		24 Months Ended
	Sep. 30, 2020 USD ($) ft² unit	Sep. 30, 2019 USD ($)	Sep. 30, 2020 USD ($) ft² unit	Sep. 30, 2019 USD ($)	Sep. 30, 2020 USD ($) ft² unit
Real Estate [Line Items]
Net gain on sale of real estate			$ 0	$ 2,571,099
Income tax expense	$ 23,781	$ 23,885	$ 38,431	$ 80,542
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	$ 1,436,000		$ 1,436,000		$ 1,436,000
Number of condominium units sold (unit) | unit	19		30		95
Cash proceeds from the sale of real estate	$ 591,104		$ 939,292		$ 2,759,424
Net gain on sale of real estate	214,578		338,862		$ 1,024,479
Income tax expense	$ 27,669		$ 43,037