Segment Information (Net Income to NOI Reconciliation) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Segment Reporting [Abstract]
Net income (loss)	$ 76,832	$ (217,352)	$ 103,825	$ (321,855)
Depreciation and amortization expense	89,777	92,805	185,131	185,598
General and administrative expense	30,602	35,014	74,788	87,848
Transaction related costs and other (lease liability extinguishment gain)	106	(69,221)	949	(69,150)
(Income) loss from partially owned entities	(31,426)	291,873	(60,499)	272,770
(Income) loss from real estate fund investments	(5,342)	28,042	(5,173)	211,505
Interest and other investment (income) loss, net	(1,539)	2,893	(3,061)	8,797
Interest and debt expense	51,894	58,405	101,958	117,247
Net gains on disposition of wholly owned and partially owned assets	(25,724)	(55,695)	(25,724)	(124,284)
Income tax expense	2,841	1,837	4,825	14,650
NOI from partially owned entities	77,235	69,487	155,991	151,368
NOI attributable to noncontrolling interests in consolidated subsidiaries	(15,689)	(15,448)	(33,335)	(30,941)
NOI at share	249,567	222,640	499,675	503,553
Non cash adjustments for straight-line rents, amortization of acquired below-market leases, net and other	846	34,190	(352)	37,266
NOI at share - cash basis	$ 250,413	$ 256,830	$ 499,323	$ 540,819