Real Estate and Other Affiliates (Relevant Financial Information) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Jun. 30, 2020	Dec. 31, 2019	Jun. 30, 2019	Dec. 31, 2018
Real Estate and Other Affiliates
Total Assets	$ 9,041,245		$ 9,041,245			$ 8,413,766
Total Liabilities	5,297,222		5,297,222			5,080,778
Total Equity	3,713,662	$ 3,380,056	3,713,662	$ 3,380,056	$ 3,739,703	3,332,988	$ 3,351,767	$ 3,238,126
Revenues	154,440	231,172	485,788	1,016,378
Net income (loss)	164,002	30,043	4,817	75,296
Equity Method Investment, Nonconsolidated Investee or Group of Investees | The Summit
Real Estate and Other Affiliates
Total Assets	274,835		274,835			221,277
Total Liabilities	187,375		187,375			136,314
Total Equity	87,460		87,460			$ 84,963
Revenues	37,350	25,931	96,022	84,118
Net income (loss)	(1,563)	4,523	6,028	18,859
Gross Margin	$ 245	$ 5,587	$ 10,501	$ 22,334