CONSOLIDATED STATEMENTS OF CASH FLOWS $ in Thousands	12 Months Ended
	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)
CASH FLOWS FROM OPERATING ACTIVITIES:
Net income	$ 628,381	$ 4,480,104	$ 908,018
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation	743,749	705,649	765,895
Amortization of deferred financing costs	8,526	12,633	10,801
Amortization of above/below market lease intangibles	3,828	3,426	3,382
Amortization of discounts and premiums on debt	3,536	(17,986)	(10,569)
Amortization of deferred settlements on derivative instruments	18,847	41,680	18,075
Impairment	1,693	0	0
Write-off of pursuit costs	3,106	4,092	2,878
(Income) loss from investments in unconsolidated entities	3,370	(4,801)	(15,025)
Distributions from unconsolidated entities – return on capital	2,632	2,863	4,741
Net (gain) loss on sales of investment securities and other investments	0	(58,409)	(526)
Net (gain) loss on sales of real estate properties	(157,057)	(4,044,055)	(335,134)
Net (gain) loss on sales of land parcels	(19,167)	(15,731)	1
Net (gain) loss on sales of discontinued operations	0	(43)	0
Net (gain) loss on debt extinguishment	12,258	114,666	0
Realized/unrealized (gain) loss on derivative instruments	0	74	3,055
Compensation paid with Company Common Shares	24,997	30,530	34,607
Changes in assets and liabilities:
(Increase) decrease in other assets	(449)	31,147	(41,803)
Increase (decrease) in accounts payable and accrued expenses	11,532	(6,061)	(1,667)
Increase (decrease) in accrued interest payable	(2,911)	(24,275)	(4,319)
Increase (decrease) in other liabilities	(23,468)	(26,422)	12,269
Increase (decrease) in security deposits	2,385	(14,958)	1,949
Net cash provided by operating activities	1,265,788	1,214,123	1,356,628
CASH FLOWS FROM INVESTING ACTIVITIES:
Investment in real estate – acquisitions	(466,394)	(205,880)	(331,336)
Investment in real estate – development/other	(276,382)	(566,825)	(653,897)
Capital expenditures to real estate	(202,607)	(172,177)	(182,113)
Non-real estate capital additions	(1,506)	(5,731)	(3,991)
Interest capitalized for real estate under development	(26,290)	(51,451)	(59,885)
Proceeds from disposition of real estate, net	384,583	6,824,659	504,748
Investments in unconsolidated entities	(6,034)	(5,266)	(23,019)
Distributions from unconsolidated entities – return of capital	334	13,798	51,144
Proceeds from sale of investment securities and other investments	0	72,815	2,535
Net cash provided by (used for) investing activities	(594,296)	5,903,942	(695,814)
CASH FLOWS FROM FINANCING ACTIVITIES:
Debt financing costs	(6,289)	(13,305)	(6,425)
Mortgage notes payable, net:
Lump sum payoffs	(493,420)	(583,122)	(359,244)
Scheduled principal repayments	(10,704)	(8,544)	(9,275)
Notes, net:
Proceeds	692,466	496,705	746,391
Lump sum payoffs	(497,975)	(1,500,000)	(300,000)
Line of credit and commercial paper:
Line of credit proceeds	1,845,000	426,000	3,770,000
Line of credit repayments	(1,845,000)	(426,000)	(4,103,000)
Commercial paper proceeds	5,066,509	1,760,194	3,932,304
Commercial paper repayments	(4,786,750)	(2,127,472)	(3,545,028)
Proceeds from (payments on) settlement of derivative instruments	1,295	(4,662)	(13,938)
Proceeds from Employee Share Purchase Plan (ESPP)	3,744	3,686	4,404
Proceeds from exercise of options	31,596	35,833	59,508
Redemption of Preferred Shares	0	0	(12,720)
Premium on redemption of Preferred Shares	0	0	(3,486)
Payment of offering costs	(51)	(314)	(79)
Other financing activities, net	(63)	(49)	(49)
Contributions – Noncontrolling Interests – Partially Owned Properties	125	0	0
Contributions – Noncontrolling Interests – Operating Partnership	0	1	3
Distributions:
Common Shares	(739,375)	(4,771,725)	(784,748)
Preferred Shares	(3,091)	(2,318)	(3,357)
Noncontrolling Interests – Operating Partnership	(27,291)	(188,115)	(30,869)
Noncontrolling Interests – Partially Owned Properties	(8,286)	(36,219)	(6,559)
Net cash provided by (used for) financing activities	(789,818)	(7,054,092)	(666,167)
Net increase (decrease) in cash and cash equivalents and restricted deposits	(118,326)	63,973	(5,353)
Cash and cash equivalents and restricted deposits, beginning of year	219,088	155,115	160,468
Cash and cash equivalents and restricted deposits, end of year	100,762	219,088	155,115
Cash and cash equivalents	50,647	77,207	42,276
Restricted deposits	50,115	141,881	112,839
SUPPLEMENTAL INFORMATION:
Cash paid for interest, net of amounts capitalized	360,273	482,152	436,748
Net cash paid for income and other taxes	640	1,494	1,264
Real estate acquisitions/dispositions/other:
Mortgage loans assumed	0	43,400	0
Amortization of deferred financing costs:
Other assets	2,412	3,366	3,054
Mortgage notes payable, net	2,493	3,978	3,589
Notes, net	3,621	5,289	4,158
Amortization of discounts and premiums on debt:
Mortgage notes payable, net	1,172	(21,158)	(13,126)
Notes, net	2,364	3,172	2,557
Amortization of deferred settlements on derivative instruments:
Other liabilities	(11)	(78)	(169)
Accumulated other comprehensive income	18,858	41,758	18,244
Write-off of pursuit costs:
Investment in real estate, net	2,965	3,586	2,804
Other assets	17	402	74
Accounts payable and accrued expenses	124	104	0
(Income) loss from investments in unconsolidated entities:
Investments in unconsolidated entities	1,955	(6,327)	(17,340)
Other liabilities	1,415	1,526	2,315
Distributions from unconsolidated entities – return on capital:
Investments in unconsolidated entities	2,632	2,863	4,606
Other liabilities	0	0	135
Realized/unrealized (gain) loss on derivative instruments:
Other assets	(4,582)	1,798	(3,573)
Notes, net	(3,454)	(1,798)	2,058
Other liabilities	1,597	3,989	2,351
Accumulated other comprehensive income	6,439	(3,915)	2,219
Investments in unconsolidated entities:
Investments in unconsolidated entities	(3,034)	(2,326)	(1,404)
Other liabilities	(3,000)	(2,940)	(21,615)
Distributions from unconsolidated entities - return of capital:
Investments in unconsolidated entities	334	14,014	51,144
Other assets	0	(216)	0
Debt financing costs:
Other assets	0	(8,553)	0
Mortgage notes payable, net	0	(507)	(35)
Notes, net	(6,289)	(4,245)	(6,390)
Proceeds from (payments on) settlement of derivative instruments:
Other assets	1,295	0	1,848
Other liabilities	0	(4,662)	(15,786)
Other:
Foreign currency translation adjustments	0	(264)	327
Notes, Net [Member]
CASH FLOWS FROM FINANCING ACTIVITIES:
Net gain (loss) on debt extinguishment	0	(82,934)	0
Mortgage Notes Payable, Net [Member]
CASH FLOWS FROM FINANCING ACTIVITIES:
Net gain (loss) on debt extinguishment	$ (12,258)	$ (31,732)	$ 0