CONSOLIDATED STATEMENTS OF CASH FLOWS (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
CASH FLOWS FROM OPERATING ACTIVITIES:
Net income	$ 1,061,034	$ 152,167
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation	220,038	175,108
Amortization of deferred financing costs	7,176	2,974
Amortization of Intangible Assets	292	0
Amortization of discounts and premiums on debt	(7,071)	(1,567)
Amortization of deferred settlements on derivative instruments	8,139	3,429
Write-off of pursuit costs	2,533	1,034
Income Loss from Investments in Unconsolidated Entities Adjustment	46,366	0
Distributions from unconsolidated entities - return on capital	257	89
Net (gain) on sales of discontinued operations	(1,198,922)	(132,956)
Unrealized (gain) loss on derivative instruments	0	(1)
Compensation paid with Company Common Shares	10,236	8,968
Changes in assets and liabilities:
(Increase) decrease in deposits - restricted	(1,733)	2,768
Increase (decrease) in mortgage deposits	1,651	(782)
(Increase) in other assets	(15,220)	(12,262)
Increase in accounts payable and accrued expenses	47,498	41,616
(Decrease) in accrued interest payable	1,039	(8,632)
Increase (decrease) in other liabilities	(18,437)	(16,878)
Increase in security deposits	(5,268)	182
Net cash provided by operating activities	193,514	234,245
CASH FLOWS FROM INVESTING ACTIVITIES:
Payments to Acquire Businesses, Net of Cash Acquired	(4,000,643)	0
Investment in real estate – acquisitions	0	183,112
Investment in real estate - development/other	(65,232)	(35,876)
Improvements to real estate	(26,599)	(30,225)
Additions to non-real estate property	(1,942)	(2,229)
Interest capitalized for real estate and unconsolidated entities under development	(8,413)	(4,996)
Proceeds from disposition of real estate, net	2,955,398	204,272
Investments in unconsolidated entities	(283)	(2,396)
(Increase) in deposits on real estate acquisitions and investments, net	101,668	(27,386)
Decrease in mortgage deposits	4,473	83
Net cash (used for) provided by investing activities	(1,041,573)	(81,865)
CASH FLOWS FROM FINANCING ACTIVITIES:
Loan and bond acquisition costs	(13,869)	(4,227)
Mortgage Deposits	632	37
Mortgage notes payable:
Restricted cash	0	209
Lump sum payoffs	(584,020)	(47,800)
Scheduled principal repayments	(3,244)	(3,970)
Notes, net:
Proceeds from Notes Payable	750,000	0
Lump sum payoffs	0	(253,858)
Line of Credit Facility:
Proceeds	(5,850,000)	0
Repayments	(5,455,000)	0
Proceeds from sale of Common Shares	0	152,058
Proceeds from Employee Stock Purchase Plan (ESPP)	(1,763)	(4,210)
Proceeds from exercise of options	(7,174)	(18,938)
Payment of offering costs	(406)	(1,887)
Contributions - Noncontrolling Interests - Partially Owned Properties	(3,299)	(921)
Contributions - Noncontrolling Interests - Operating Partnership	(3)	(5)
Distributions:
Common Shares	(249,330)	(168,350)
Preferred Shares	0	(3,466)
Noncontrolling Interests – Operating Partnership	(10,837)	(7,657)
Noncontrolling Interests – Partially Owned Properties	(3,345)	(1,762)
Net cash (used for) financing activities	291,556	(316,673)
Net (decrease) increase in cash and cash equivalents	(556,503)	(164,293)
Cash and cash equivalents, beginning of period	612,590	383,921
Cash and cash equivalents, end of period	56,087	219,628
SUPPLEMENTAL INFORMATION:
Cash paid for interest, net of amounts capitalized	182,356	125,435
Net cash paid for income and other taxes	483	560
AmortizationOfDeferredFinancingCosts [Abstract]
Amortization Of Deferred Financing Costs Investment In Real Estate Net	(1)	0
Amortization Of Deferred Financing Costs Deferred Financing Costs Net	7,177	2,974
Amortization of discounts and premiums on debt:
Mortgage notes payable	(7,557)	(2,153)
Notes, net	486	586
Amortization of deferred settlements on derivative instruments:
Other liabilities	(133)	(134)
Accumulated other comprehensive income	(8,272)	(3,563)
Loss From Investments In Unconsolidated Entities [Abstract]
Income Loss From Equity Method Investments Merger	42,213	0
Other Liabilities Loss From Investments in unconsolidated entities	4,153	0
Unrealized (gain) loss on derivative instruments:
Other assets	1,471	1,300
Mortgage notes payable	0	(588)
Notes, net	(1,471)	(712)
Other liabilities	(2,814)	(3,219)
Unrealized holding (losses) arising during the period	2,814	3,218
Acquisition of Archstone, net of cash acquired [Abstract]
Acquisition of Archstone Investment in real estate, net	(8,707,967)	0
Acquisition of Archstone Investments in Unconsolidated Entities	(218,197)	0
Acquisition of Archstone Restricted Cash and Cash Equivalents	(474)	0
Acquisition of Archstone Escrow Deposits For Mortgage And Replacement Reserves	(35,898)	0
Acquisition of Archstone Deferred Finance Costs, Net	(25,780)	0
Acquisition of Archstone Other Assets	(204,523)	0
Acquisition of Archstone Secured Debt	3,076,876	0
Acquisition of Archstone Accounts Payable And Accrued Liabilities	17,593	0
Acquisition of Archstone Interest Payable	11,256	0
Acquisition of Archstone Other Liabilities	117,391	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	(8,089)	(4,827)
Investment in unconsolidated entities	(324)	(169)
Other:
Receivable For Common Shares Issued	0	28,457
Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Gain (Loss) Arising During Period, Net of Tax	$ 873	$ 0