CONSOLIDATED STATEMENTS OF CASH FLOWS (USD $) In Thousands, unless otherwise specified	9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012
CASH FLOWS FROM OPERATING ACTIVITIES:
Net income	$ 1,789,483	$ 496,805
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation	830,097	516,940
Amortization of deferred financing costs	15,864	10,384
Amortization of Intangible Assets	2,214	0
Amortization of discounts and premiums on debt	(37,612)	(5,795)
Amortization of deferred settlements on derivative instruments	15,683	10,506
Write-off of pursuit costs	3,969	6,141
Income Loss from Investments in Unconsolidated Entities Adjustment	57,765	3
Distributions from unconsolidated entities - return on capital	1,519	454
(Gain) Loss on Sale of Securities, Net	(830)	0
Net Gain on Sales of Unconsolidated Entities	(16)	0
Net (gain) on sales of land parcels	(12,179)	0
Net (gain) on sales of discontinued operations	(1,990,577)	(307,447)
Unrealized (gain) loss on derivative instruments	32	(1)
Compensation paid with Company Common Shares	29,019	20,836
Changes in assets and liabilities:
(Increase) decrease in deposits - restricted	4,152	(2,250)
(Increase) decrease in mortgage deposits	271	(862)
(Increase) decrease in other assets	7,315	(14,039)
Increase in accounts payable and accrued expenses	65,001	67,479
(Decrease) in accrued interest payable	(2,175)	(9,252)
Increase (decrease) in other liabilities	(5,427)	68,492
(Decrease) increase in security deposits	(6,475)	3,472
Net cash provided by operating activities	767,093	861,866
CASH FLOWS FROM INVESTING ACTIVITIES:
Payments to Acquire Businesses, Net of Cash Acquired	(4,000,875)	0
Investment in real estate – acquisitions	(108,308)	(764,859)
Investment in real estate - development/other	(256,965)	(116,715)
Improvements to real estate	(96,866)	(114,535)
Additions to non-real estate property	(3,359)	(6,716)
Interest capitalized for real estate and unconsolidated entities under development	(32,946)	(15,776)
Proceeds from disposition of real estate, net	4,434,708	610,127
Investments in unconsolidated entities	(59,363)	(5,423)
Proceeds From Distributions Received From Unconsolidated Subsidiaries	25,471	0
Proceeds from Sale of Available-for-sale Securities	828	0
Decrease in deposits on real estate acquisitions and investments, net	147,890	31,677
Decrease in mortgage deposits	7,623	1,682
Acquisition of Noncontrolling Interests – Partially Owned Properties	0	(87)
Net cash (used for) provided by investing activities	57,838	(380,625)
CASH FLOWS FROM FINANCING ACTIVITIES:
Loan and bond acquisition costs	(18,254)	(4,599)
Mortgage Deposits	(3,769)	(590)
Mortgage notes payable:
Proceeds from Issuance of Long-term Debt	5,951	0
Restricted cash	0	2,370
Lump sum payoffs	(701,762)	(279,943)
Scheduled principal repayments	(9,527)	(11,022)
Notes, net:
Proceeds from Notes Payable	1,245,550	0
Lump sum payoffs	(400,000)	(253,858)
Line of Credit Facility:
Proceeds	8,413,000	392,000
Repayments	(8,413,000)	(385,000)
Payments for (Proceeds from) Hedge, Financing Activities	(44,013)	0
Proceeds from sale of Common Shares	0	220,753
Proceeds from Employee Stock Purchase Plan	2,973	4,944
Proceeds from exercise of options	16,044	46,781
Redemption of Preferred Shares	0	(150,000)
Premium On Redemption Of Preferred Shares Cash	0	(21)
Payment of offering costs	(954)	(2,860)
Proceeds from (Payments for) Other Financing Activities	(33)	(33)
Contributions - Noncontrolling Interests - Partially Owned Properties	11,520	5,992
Contributions - Noncontrolling Interests - Operating Partnership	5	5
Distributions:
Common Shares	(537,464)	(371,319)
Preferred Shares	(3,109)	(11,344)
Noncontrolling Interests – Operating Partnership	(22,216)	(17,053)
Noncontrolling Interests – Partially Owned Properties	(5,702)	(4,742)
Net cash (used for) financing activities	(464,760)	(819,539)
Net (decrease) increase in cash and cash equivalents	360,171	(338,298)
Cash and cash equivalents, beginning of period	612,590	383,921
Cash and cash equivalents, end of period	972,761	45,623
SUPPLEMENTAL INFORMATION:
Cash paid for interest, net of amounts capitalized	451,495	353,329
Net cash paid for income and other taxes	1,064	573
Real estate acquisitions/dispositions/other:
Mortgage loans assumed	0	137,644
Valuation Of O P Units Issued	0	66,606
AmortizationOfDeferredFinancingCosts [Abstract]
Amortization Of Deferred Financing Costs Investment In Real Estate Net	(152)	0
Amortization Of Deferred Financing Costs Deferred Financing Costs Net	16,016	10,384
Amortization of discounts and premiums on debt:
Mortgage notes payable	(39,232)	(7,462)
Notes, net	1,620	1,667
Amortization of deferred settlements on derivative instruments:
Other liabilities	(401)	(401)
Losses reclassified into earnings from other comprehensive income	16,084	10,907
Loss From Investments In Unconsolidated Entities [Abstract]
Income Loss From Equity Method Investments Merger	51,923	3
Other Liabilities Loss From Investments in unconsolidated entities	5,842	0
Unrealized (gain) loss on derivative instruments:
Other assets	(10,609)	5,934
Mortgage notes payable	0	(2,589)
Notes, net	(1,523)	(3,345)
Other liabilities	3,427	12,336
Unrealized holding gains (losses) arising during the period	8,737	(12,337)
Acquisition of Archstone, net of cash acquired [Abstract]
Acquisition of Archstone Investment in Real Estate Net	(8,710,242)	0
Acquisition of Archstone Investments in Unconsolidated Entities	(217,092)	0
Acquisition of Archstone Deposits Restricted	(474)	0
Acquisition of Archstone Escrow Deposits Mortgage	(35,897)	0
Acquisition of Archstone Deferred Financing Costs	(25,780)	0
Acquisition of Archstone Other Assets	(203,295)	0
Acquisition of Archstone Mortgage Notes Payable	3,076,876	0
Acquisition of Archstone Accounts Payable And Accrued Liabilities	17,576	0
Acqusition of Archstone Interest Payable	11,305	0
Acquisition of Archstone Other Liabilities	117,068	0
Acquisition of Archstone Security Deposits	10,949	0
Acquisition of Archstone Common Shares Issued	1,929,868	0
Acquisition of Archstone Noncontrolling Interests Partially Owned Properties	28,263	0
Interest capitalized for real estate and unconsolidated entities under development:
Investment in real estate, net	(31,648)	(15,163)
Investment in unconsolidated entities	(1,298)	(613)
Equity Method Investments and Joint Ventures [Abstract]
Investments in unconsolidated entities	(9,317)	(5,423)
Investments in unconsolidated entities other liabilities	(50,046)	0
Other:
Receivable For Common Shares OP Units Issued	0	28,457
Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Gain (Loss) Arising During Period, Net of Tax	$ 789	$ 0