Real Estate and Other Affiliates (Relevant Financial Information for the Summit) (Details) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021 USD ($)	Sep. 30, 2020 USD ($)	Sep. 30, 2021 USD ($) condominium_unit	Sep. 30, 2020 USD ($) condominium_unit	Jun. 30, 2021 USD ($)	Dec. 31, 2020 USD ($)	Jun. 30, 2020 USD ($)	Dec. 31, 2019 USD ($)
Investments in and Advances to Affiliates [Line Items]
Total assets	$ 9,514,913		$ 9,514,913			$ 9,140,332
Total liabilities	5,806,929		5,806,929			5,396,195
Total equity	3,682,584	$ 3,713,662	3,682,584	$ 3,713,662	$ 3,671,903	3,715,023	$ 3,739,703	$ 3,332,988
Revenues	219,188	154,440	622,225	485,788
Operating income (loss)	49,135	(14,009)	39,718	(151,640)
Net income (loss)	2,117	$ 164,002	(62,425)	4,817
The Summit
Investments in and Advances to Affiliates [Line Items]
Total assets	226,600		226,600			310,855
Total liabilities	175,960		175,960			209,968
Total equity	50,640		50,640			100,887
Revenues			260,398	96,022
Gross margin			87,837	10,501
Operating income (loss)			0
Net income (loss)			$ 85,925	$ 6,028
Number of units closed | condominium_unit			43	19
110 North Wacker
Investments in and Advances to Affiliates [Line Items]
Total assets	677,419		$ 677,419			634,274
Total liabilities	484,721		484,721			415,452
Total equity	$ 192,698		192,698			$ 218,822
Revenues			22,279	$ 0
Gross margin			0	0
Operating income (loss)			13,811
Net income (loss)			$ (32,597)	$ 0