CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
CASH FLOWS FROM OPERATING ACTIVITIES:
Net income	$ 4,480,104	$ 908,018	$ 658,683
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation	705,649	765,895	758,861
Amortization of deferred financing costs	12,633	10,801	11,088
Amortization of above/below market leases	3,426	3,382	3,222
Amortization of discounts and premiums on debt	(17,378)	(9,492)	(13,520)
Amortization of deferred settlements on derivative instruments	41,680	18,075	16,334
Write-off of pursuit costs	4,092	3,208	3,607
(Income) loss from investments in unconsolidated entities	(4,801)	(15,025)	7,952
Distributions from unconsolidated entities – return on capital	2,863	4,741	5,570
Net (gain) on sales of investment securities and other investments	(58,409)	(526)	(57)
Net (gain) on sales of real estate properties	(4,044,055)	(335,134)	(212,685)
Net (gain) loss on sales of land parcels	(15,731)	1	(5,277)
Net (gain) on sales of discontinued operations	(43)	0	(179)
Realized/unrealized loss (gain) on derivative instruments	74	3,055	(60)
Compensation paid with Company Common Shares	30,530	34,607	27,543
Changes in assets and liabilities:
Decrease (increase) in deposits – restricted	11,450	(1,794)	(1,740)
(Increase) decrease in mortgage deposits	(26)	258	1,452
Decrease (increase) in other assets	31,147	(41,803)	21,773
(Decrease) increase in accounts payable and accrued expenses	(6,061)	(1,667)	17,797
(Decrease) increase in accrued interest payable	(24,275)	(4,319)	11,231
(Decrease) increase in other liabilities	(26,422)	12,269	8,437
(Decrease) increase in security deposits	(14,958)	1,949	4,041
Net cash provided by operating activities	1,111,489	1,356,499	1,324,073
CASH FLOWS FROM INVESTING ACTIVITIES:
Investment in real estate – acquisitions	(205,880)	(331,336)	(469,989)
Investment in real estate – development/other	(566,825)	(653,897)	(530,387)
Capital expenditures to real estate	(172,177)	(182,113)	(185,957)
Non-real estate capital additions	(5,731)	(3,991)	(5,286)
Interest capitalized for real estate and unconsolidated entities under development	(51,451)	(59,885)	(52,782)
Proceeds from disposition of real estate, net	6,824,659	504,748	522,647
Investments in unconsolidated entities	(5,266)	(23,019)	(15,768)
Distributions from unconsolidated entities – return of capital	13,798	51,144	103,793
Proceeds from sale of investment securities and other investments	72,815	2,535	57
(Increase) decrease in deposits on real estate acquisitions and investments, net	(32,503)	17,874	33,004
Decrease (increase) in mortgage deposits	534	(531)	798
Consolidation of previously unconsolidated properties	0	0	(44,796)
Net cash provided by (used for) investing activities	5,871,973	(678,471)	(644,666)
CASH FLOWS FROM FINANCING ACTIVITIES:
Debt financing costs	(13,305)	(6,425)	(10,982)
Mortgage deposits	(8,497)	(8,588)	(7,699)
Mortgage notes payable:
Lump sum payoffs	(583,122)	(359,244)	(88,788)
Scheduled principal repayments	(8,544)	(9,275)	(11,869)
Notes, net:
Proceeds	496,705	746,391	1,194,277
Lump sum payoffs	(1,500,000)	(300,000)	(1,250,000)
Line of credit and commercial paper:
Line of credit proceeds	426,000	3,770,000	7,167,000
Line of credit repayments	(426,000)	(4,103,000)	(6,949,000)
Commercial paper proceeds	1,759,586	3,931,227	0
Commercial paper repayments	(2,127,472)	(3,545,028)	0
(Payments on) settlement of derivative instruments	(4,662)	(13,938)	(758)
Proceeds from Employee Share Purchase Plan (ESPP)	3,686	4,404	3,392
Proceeds from exercise of options	35,833	59,508	82,573
Common Shares repurchased and retired	0	0	(1,777)
Redemption of Preferred Shares	0	(12,720)	0
Premium on redemption of Preferred Shares	0	(3,486)	0
Payment of offering costs	(314)	(79)	(41)
Other financing activities, net	(49)	(49)	(49)
Acquisition of Noncontrolling Interests – Partially Owned Properties	0	0	(5,501)
Contributions – Noncontrolling Interests – Partially Owned Properties	0	0	5,684
Contributions – Noncontrolling Interests – Operating Partnership	1	3	3
Distributions:
Common Shares	(4,771,725)	(784,748)	(776,659)
Preferred Shares	(2,318)	(3,357)	(4,145)
Noncontrolling Interests – Operating Partnership	(188,115)	(30,869)	(30,744)
Noncontrolling Interests – Partially Owned Properties	(36,219)	(6,559)	(7,778)
Net cash (used for) financing activities	(6,948,531)	(675,832)	(692,861)
Net increase (decrease) in cash and cash equivalents	34,931	2,196	(13,454)
Cash and cash equivalents, beginning of year	42,276	40,080	53,534
Cash and cash equivalents, end of year	77,207	42,276	40,080
SUPPLEMENTAL INFORMATION:
Cash paid for interest, net of amounts capitalized	482,152	436,748	443,125
Net cash paid for income and other taxes	1,494	1,264	1,517
Real estate acquisitions/dispositions/other:
Mortgage loans assumed	43,400	0	28,910
Amortization of deferred financing costs:
Other assets	3,366	3,054	3,054
Mortgage notes payable, net	3,978	3,589	3,075
Notes, net	5,289	4,158	4,959
Amortization of discounts and premiums on debt:
Mortgage notes payable	(21,158)	(13,126)	(15,904)
Notes, net	3,172	2,557	2,384
Line of credit and commercial paper	608	1,077	0
Amortization of deferred settlements on derivative instruments:
Other liabilities	(78)	(169)	(534)
Accumulated other comprehensive income	41,758	18,244	16,868
Write-off of pursuit costs [Abstract]
Investment in real estate, net	3,586	2,804	2,541
Deposits – restricted	0	330	0
Other assets	402	74	1,066
Accounts payable and accrued expenses	104	0	0
(Income) loss from investments in unconsolidated entities:
Investments in unconsolidated entities	(6,327)	(17,340)	4,610
Other liabilities	1,526	2,315	3,342
Distributions from unconsolidated entities return on capital:
Investments in unconsolidated entities	2,863	4,606	5,360
Other liabilities	0	135	210
Realized/unrealized loss (gain) on derivative instruments:
Other assets	1,798	(3,573)	10,160
Notes, net	(1,798)	2,058	1,597
Other liabilities	3,989	2,351	21,489
Accumulated other comprehensive income	(3,915)	2,219	(33,306)
Interest capitalized for real estate and unconsolidated entities under development:
Investment in real estate, net	(51,451)	(59,885)	(52,717)
Investments in unconsolidated entities	0	0	(65)
Investments in unconsolidated entities:
Investments in unconsolidated entities	(2,326)	(1,404)	(6,318)
Other liabilities	(2,940)	(21,615)	(9,450)
Distributions from unconsolidated entities - return of capital:
Investments in unconsolidated entities	14,014	51,144	103,793
Other assets	(216)	0	0
Consolidation of previously unconsolidated properties:
Investment in real estate, net	205,880	331,336	469,989
Investments in unconsolidated entities	(5,266)	(23,019)	(15,768)
Accounts payable and accrued expenses	(6,061)	(1,667)	17,797
Debt financing costs:
Other assets	(8,553)	0	0
Mortgage notes payable, net	(507)	(35)	(448)
Notes, net	(4,245)	(6,390)	(10,534)
(Payments on) settlement of derivative instruments:
Other assets	0	1,848	6,623
Other liabilities	(4,662)	(15,786)	(7,381)
Other:
Foreign currency translation adjustments	(264)	327	552
Partially Owned Properties – Unconsolidated
Changes in assets and liabilities:
(Decrease) increase in accounts payable and accrued expenses	0	0	1,987
CASH FLOWS FROM INVESTING ACTIVITIES:
Investment in real estate – acquisitions	0	0	64,319
Investments in unconsolidated entities	0	0	(847)
Consolidation of previously unconsolidated properties:
Investment in real estate, net	0	0	(64,319)
Investments in unconsolidated entities	0	0	(847)
Accounts payable and accrued expenses	0	0	1,987
Other Liabilities	$ 0	$ 0	$ 18,383