Segment Information (Summary of net income and EBITDA reconciliation by segment) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Segment Reporting [Abstract]
Net (loss) income	$ (104,503)	$ 213,044
Depreciation and amortization expense	92,793	116,709
General and administrative expense	52,834	58,020
Transaction related costs, impairment losses and other	71	149
Income from partially owned entities	(19,103)	(7,320)
Loss from real estate fund investments	183,463	167
Interest and other investment loss (income), net	5,904	(5,045)
Interest and debt expense	58,842	102,463
Net gains on disposition of wholly owned and partially owned assets	(68,589)	(220,294)
Income tax expense	12,813	29,743
Loss from discontinued operations	0	137
NOI from partially owned entities	81,881	67,402
NOI attributable to noncontrolling interests in consolidated subsidiaries	(15,493)	(17,403)
NOI at share	280,913	337,772
Non cash adjustments for straight-line rents, amortization of acquired below-market leases, net and other	3,076	(5,181)
NOI at share - cash basis	$ 283,989	$ 332,591