Segment Information (Summary of net income and EBITDA reconciliation by segment) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Segment Information
Net income	$ 282	$ 73,847
Loss (income) from partially owned entities	9,904	(1,358)
Loss (income) from real estate fund investments	8,807	(268)
Interest and other investment loss (income), net	24,384	(6,695)
Net gains on disposition of wholly owned and partially owned assets	0	(501)
(Loss) income from discontinued operations	363	(15,318)
NOI attributable to noncontrolling interests in consolidated subsidiaries	(17,312)	(16,338)
Depreciation and amortization expense	108,686	105,128
General and administrative expense	43,633	47,237
Transaction related costs and other	13,156	752
NOI from partially owned entities	67,513	66,097
Interest and debt expense	88,166	82,724
Income tax expense	1,454	1,851
NOI at share	349,036	337,158
Non-cash adjustments for straight-line rents, amortization of acquired below-market leases, net and other	(17,948)	(20,481)
NOI at share - cash basis	331,088	316,677
Real estate fund investments
Segment Information
Loss (income) from real estate fund investments	$ 8,807	$ (268)