Consolidated Statements of Cash Flows - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Operating activities
Net income (loss)		$ 540,613	$ 1,082,070	$ 888,549
Adjustments to reconcile net income to net cash provided from (used in) operating activities:
Depreciation and amortization expenses		921,720	901,242	826,240
Other amortization expenses		16,521	8,822	4,991
Provision for loan losses		62,966	10,215	0
Impairment of assets		124,483	37,207	2,220
Stock-based compensation expense		19,102	28,869	30,844
Loss on derivatives		2,284	(2,448)	(58,427)
Loss (gain) on extinguishment of debt, net		37,241	17,214	34,677
Income from unconsolidated entities		83,125	10,357	21,504
Rental income less than (in excess of) cash received		(80,398)	(83,233)	(115,756)
Amortization related to above (below) market leases, net		357	322	4,018
Loss (Gain) on sale of properties, net		(344,250)	(364,046)	(280,387)
Other (income) expense		2	(4,853)	31,979
Distributions by unconsolidated entities operating		116	1,065	637
Increase (decrease) in accrued expenses and other liabilities		26,809	14,298	(8,968)
Decrease (increase) in receivables and other assets		23,486	(18,037)	478
Net cash provided from (used in) operating activities		1,434,177	1,639,064	1,382,599
Investing activities
Cash disbursed for acquisitions		(805,264)	(2,145,374)	(3,353,087)
Cash disbursed for capital improvements to existing properties		(250,276)	(219,146)	(187,752)
Cash disbursed for construction in progress		(232,715)	(403,131)	(244,561)
Capitalized interest		(13,489)	(16,943)	(8,670)
Investment in real estate loans receivable		(83,738)	(129,884)	(598,722)
Other investments, net of payments		57,385	4,760	(141,994)
Principal collected on real estate loans receivable		96,023	249,552	131,830
Contributions to unconsolidated entities		(114,365)	(101,415)	(160,323)
Distributions by unconsolidated entities investing		70,287	119,723	130,880
Proceeds from (payments on) derivatives investing		52,719	108,347	106,360
Proceeds from sales of real property		1,378,014	2,350,068	823,964
Net cash provided from (used in) investing activities		154,581	(183,443)	(3,502,075)
Financing activities
Net increase (decrease) under unsecured lines of credit arrangements		74,000	(190,000)	835,000
Proceeds from issuance of senior unsecured notes		7,500	693,560	1,451,434
Payments to extinguish senior unsecured notes		(5,000)	(865,863)	(558,830)
Net proceeds from the issuance of secured debt		241,772	460,015	228,685
Payments on secured debt		(1,144,346)	(563,759)	(573,390)
Net proceeds from the issuance of common stock		621,987	534,194	1,755,722
Redemption of preferred stock		(287,500)	0	0
Decrease (increase) in deferred loan expenses		(54,333)	(22,196)	(11,513)
Contributions by noncontrolling interests	[1]	56,560	148,666	173,018
Distributions to noncontrolling interests	[1]	(87,711)	(134,578)	(50,877)
Acquisitions of non controlling interests		0	0	(5,663)
Cash distributions to stockholders		(1,325,617)	(1,298,925)	(1,210,133)
Other financing activities		(10,839)	(11,931)	(36,135)
Net cash provided from (used in) financing activities		(1,913,527)	(1,250,817)	1,997,318
Effect of foreign currency translation on cash and cash equivalents		26,852	(20,274)	(8,575)
Increase (decrease) in cash and cash equivalents		(297,917)	184,530	(130,733)
Cash, cash equivalents and restricted cash at the beginning of period		607,220	422,690	553,423
Cash, cash equivalents and restricted cash at the end of period		309,303	607,220	422,690
Supplemental cash flow information:
Interest paid		488,265	541,545	492,771
Income taxes paid		$ 10,410	$ 8,011	$ 12,214

[1] Includes amounts attributable to redeemable noncontrolling interests.