CONSOLIDATED STATEMENTS OF CASH FLOWS (USD $)	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
CASH FLOWS FROM OPERATING ACTIVITIES:
Net income	$ 1,905,353,000	$ 881,204,000	$ 935,197,000
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation	1,013,353,000	684,992,000	663,616,000
Amortization of deferred financing costs	22,425,000	21,435,000	17,846,000
Amortization of above/below market leases	898,000	0	0
Amortization of discounts and premiums on debt	(156,439,000)	(8,181,000)	(1,478,000)
Amortization of deferred settlements on derivative instruments	19,607,000	14,144,000	3,808,000
Write-off of pursuit costs	5,184,000	9,056,000	5,075,000
Loss from Investments in Unconsolidated Entities Adjustment	58,163,000	14,000	0
Distributions from unconsolidated entities - return on capital	2,481,000	575,000	319,000
Net (Gain) on Sales of Investment Securities/Technology Investments	(4,203,000)	0	(4,537,000)
Net (gain) on sales of unconsolidated entities	(7,000)	0	0
Net (gain) loss on sales of land parcels	(12,227,000)	0	(4,217,000)
Net (gain) on sales of discontinued operations	(2,036,505,000)	(548,278,000)	(826,489,000)
Unrealized loss (gain) on derivative instruments	70,000	(1,000)	186,000
Compensation paid with Company Common Shares	35,474,000	24,832,000	21,177,000
Changes in assets and liabilities:
Decrease (increase) in deposits - restricted	3,684,000	(4,091,000)	4,523,000
Decrease in mortgage deposits	1,813,000	176,000	2,133,000
Decrease (increase) in other assets	3,742,000	(20,411,000)	(2,743,000)
Increase (decrease) in accounts payable and accrued expenses	6,229,000	(2,102,000)	332,000
(Decrease) in accrued interest payable	(9,219,000)	(11,898,000)	(10,510,000)
Increase (decrease) in other liabilities	15,401,000	2,987,000	(8,245,000)
(Decrease) increase in security deposits	(6,361,000)	1,702,000	4,474,000
Net cash provided by operating activities	868,916,000	1,046,155,000	800,467,000
CASH FLOWS FROM INVESTING ACTIVITIES:
Acquisition of Archstone, net of cash acquired	(4,000,875,000)	0	0
Investment in real estate - acquisitions	(108,308,000)	(843,976,000)	(1,441,599,000)
Investment in real estate - development/other	(377,442,000)	(180,409,000)	(120,741,000)
Improvements to real estate	(135,816,000)	(152,828,000)	(144,452,000)
Additions to non-real estate property	(4,134,000)	(8,821,000)	(7,110,000)
Interest capitalized for real estate and unconsolidated entities under development	(47,321,000)	(22,509,000)	(9,108,000)
Proceeds from disposition of real estate, net	4,551,454,000	1,049,219,000	1,500,583,000
Investments in unconsolidated entities	(66,471,000)	(5,291,000)	(2,021,000)
Distributions from unconsolidated entities – return of capital	25,471,000	0	0
Proceeds from Sale of Available-for-sale Securities	4,878,000	0	4,537,000
Decrease (increase) in deposits on real estate acquisitions and investments, net	143,694,000	(97,984,000)	7,631,000
Decrease (increase) in mortgage deposits	7,893,000	1,444,000	(479,000)
Deconsolidation of previously consolidated properties	0	0	28,360,000
Acquisition of Noncontrolling Interests - Partially Owned Properties	0	(13,000)	(12,809,000)
Net cash (used for) provided by investing activities	(6,977,000)	(261,168,000)	(197,208,000)
CASH FLOWS FROM FINANCING ACTIVITIES:
Loan and bond acquisition costs	(16,526,000)	(21,209,000)	(20,421,000)
Mortgage Deposits Financing Activities	(5,631,000)	(57,000)	247,000
Mortgage notes payable:
Proceeds from Issuance of Long-term Debt	902,886,000	26,495,000	190,905,000
Restricted cash	0	2,370,000	16,596,000
Lump sum payoffs	(2,532,682,000)	(350,247,000)	(974,956,000)
Scheduled principal repayments	(12,658,000)	(14,088,000)	(16,726,000)
Notes, net:
Proceeds	1,245,550,000	0	996,190,000
Lump sum payoffs	(400,000,000)	(975,991,000)	(575,641,000)
Lines of credit:
Proceeds	9,832,000,000	5,876,000,000	1,455,000,000
Repayments	(9,717,000,000)	(5,876,000,000)	(1,455,000,000)
(Payments on) proceeds from settlement of derivative instruments	(44,063,000)	0	(147,306,000)
Proceeds from sale of Common Shares	0	1,417,040,000	173,484,000
Proceeds from Employee Share Purchase Plan (ESPP)	3,401,000	5,399,000	5,262,000
Proceeds from exercise of options	17,252,000	49,039,000	95,322,000
Payments for Repurchase of Preferred Stock and Preference Stock	0	(150,000,000)	0
Premium on Redemption of Preferred Shares Cash	0	(23,000)	0
Payment of offering costs	(1,047,000)	(39,359,000)	(3,596,000)
Other financing activities, net	(48,000)	(48,000)	(48,000)
Contributions - Noncontrolling Interests - Partially Owned Properties	27,660,000	8,221,000	75,911,000
Contributions - Noncontrolling Interests - Operating Partnership	5,000	5,000	0
Distributions:
Common Shares	(681,610,000)	(473,451,000)	(432,023,000)
Preferred Shares	(4,145,000)	(13,416,000)	(12,829,000)
Noncontrolling Interests – Operating Partnership	(27,897,000)	(21,915,000)	(20,002,000)
Noncontrolling Interests - Partially Owned Properties	(6,442,000)	(5,083,000)	(1,115,000)
Net cash (used for) provided by financing activities	(1,420,995,000)	(556,318,000)	(650,746,000)
Net (decrease) increase in cash and cash equivalents	(559,056,000)	228,669,000	(47,487,000)
Cash and cash equivalents, beginning of year	612,590,000	383,921,000	431,408,000
Cash and cash equivalents, end of year	53,534,000	612,590,000	383,921,000
SUPPLEMENTAL INFORMATION:
Cash paid for interest, net of amounts capitalized	722,861,000	464,937,000	477,434,000
Net cash (received) paid for income and other taxes	1,152,000	673,000	645,000
Real estate acquisitions/dispositions/other:
Mortgage loans assumed	0	137,644,000	158,240,000
Valuation of OP Units issued	0	66,606,000	0
Amortization of deferred financing costs:
Amortization Of Deferred Financing Costs Investment In Real Estate Net	(152,000)	0	0
Amortization Of Deferred Financing Costs Deferred Financing Costs Net	22,577,000	21,435,000	17,846,000
Amortization of discounts and premiums on debt:
Mortgage notes payable	(158,625,000)	(10,333,000)	(8,260,000)
Notes, net	2,186,000	2,152,000	6,782,000
Amortization of deferred settlements on derivative instruments:
Other liabilities	(534,000)	(534,000)	(535,000)
Accumulated other comprehensive income	20,141,000	14,678,000	4,343,000
Loss From Investments In Unconsolidated Entities [Abstract]
Income Loss From Equity Method Investments Merger	53,073,000	14,000	0
Other Liabilities Loss From Investments in Unconsolidated Entities Merger	5,090,000	0	0
Unrealized loss (gain) on derivative instruments:
Other assets	(17,139,000)	7,448,000	6,826,000
Mortgage notes payable	0	(2,589,000)	(612,000)
Notes, net	(1,523,000)	(4,860,000)	(2,937,000)
Other liabilities	(39,000)	11,772,000	140,507,000
Accumulated other comprehensive (loss) income	18,771,000	(11,772,000)	(143,598,000)
Acquisition of Archstone, net of cash acquired [Abstract]
Acquisition of Archstone Investment in Real Estate Net	(8,687,355,000)	0	0
Acquisition of Archstone Investments in Unconsolidated Entities	(225,568,000)	0	0
Acquisition of Archstone Deposits Restricted	(528,000)	0	0
Acquisition of Archstone Escrow Deposits Mortgage	(37,582,000)	0	0
Acquisition of Archstone Deferred Financing Costs	(25,780,000)	0	0
Acquisition of Archstone Other Assets	(215,622,000)	0	0
Acquisition of Archstone Mortgage Notes Payable	3,076,876,000	0	0
Acquisition of Archstone Accounts Payable and Accrued Liabilities	16,984,000	0	0
Acqusition of Archstone Interest Payable	11,305,000	0	0
Acquisition of Archstone Other Liabilities	117,299,000	0	0
Acquisition of Archstone Security Deposits	10,965,000	0	0
Acquisition of Archstone Common Shares Issued	1,929,868,000	0	0
Acquisition of Archstone Noncontrolling Interests Partially Owned Properties	28,263,000	0	0
Interest capitalized for real estate and unconsolidated entities under development:
Investment in real estate, net	(45,533,000)	(21,661,000)	(8,785,000)
Investments in unconsolidated entities	(1,788,000)	(848,000)	(323,000)
Investments in unconsolidated entities [Abstract]
Investments in unconsolidated entities	(13,656,000)	(5,291,000)	(2,021,000)
Investments in unconsolidated entities other liabilities	(52,815,000)	0	0
Deconsolidation of previously consolidated properties:
Investment in real estate, net	0	0	35,495,000
Investments in unconsolidated entities	0	0	(7,135,000)
(Payments on) proceeds from settlement of derivative instruments:
Proceeds From Payments On Settlement Of Derivative Instruments Other Assets	(50,000)	0	0
Other liabilities	(44,013,000)	0	(147,306,000)
Other:
Receivable on sale of Common Shares	0	28,457,000	0
Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Gain (Loss) Arising During Period, Net of Tax	(613,000)	0	0
Partnership Interest [Member]
CASH FLOWS FROM OPERATING ACTIVITIES:
Net income	1,905,353,000	881,204,000	935,197,000
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation	1,013,353,000	684,992,000	663,616,000
Amortization of deferred financing costs	22,425,000	21,435,000	17,846,000
Amortization of above/below market leases	898,000	0	0
Amortization of discounts and premiums on debt	(156,439,000)	(8,181,000)	(1,478,000)
Amortization of deferred settlements on derivative instruments	19,607,000	14,144,000	3,808,000
Write-off of pursuit costs	5,184,000	9,056,000	5,075,000
Loss from Investments in Unconsolidated Entities Adjustment	(58,163,000)	(14,000)	0
Distributions from unconsolidated entities - return on capital	2,481,000	575,000	319,000
Net (Gain) on Sales of Investment Securities/Technology Investments	(4,203,000)	0	(4,537,000)
Net (gain) on sales of unconsolidated entities	(7,000)	0	0
Net (gain) on sales of discontinued operations	(2,036,505,000)	(548,278,000)	(826,489,000)
Unrealized loss (gain) on derivative instruments	70,000	(1,000)	186,000
Compensation paid with Company Common Shares	35,474,000	24,832,000	21,177,000
Changes in assets and liabilities:
Decrease (increase) in deposits - restricted	3,684,000	(4,091,000)	4,523,000
Decrease in mortgage deposits	(1,813,000)	(176,000)	(2,133,000)
Decrease (increase) in other assets	3,742,000	(20,411,000)	(2,743,000)
Increase (decrease) in accounts payable and accrued expenses	6,229,000	(2,102,000)	332,000
(Decrease) in accrued interest payable	(9,219,000)	(11,898,000)	(10,510,000)
Increase (decrease) in other liabilities	15,401,000	2,987,000	(8,245,000)
(Decrease) increase in security deposits	(6,361,000)	1,702,000	4,474,000
Net cash provided by operating activities	868,916,000	1,046,155,000	800,467,000
CASH FLOWS FROM INVESTING ACTIVITIES:
Acquisition of Archstone, net of cash acquired	(4,000,875,000)	0	0
Investment in real estate - acquisitions	(108,308,000)	(843,976,000)	(1,441,599,000)
Investment in real estate - development/other	(377,442,000)	(180,409,000)	(120,741,000)
Improvements to real estate	(135,816,000)	(152,828,000)	(144,452,000)
Additions to non-real estate property	(4,134,000)	(8,821,000)	(7,110,000)
Interest capitalized for real estate and unconsolidated entities under development	(47,321,000)	(22,509,000)	(9,108,000)
Proceeds from disposition of real estate, net	4,551,454,000	1,049,219,000	1,500,583,000
Investments in unconsolidated entities	66,471,000	5,291,000	2,021,000
Distributions from unconsolidated entities – return of capital	25,471,000	0	0
Proceeds from Sale of Available-for-sale Securities	(4,878,000)	0	(4,537,000)
Decrease (increase) in deposits on real estate acquisitions and investments, net	143,694,000	(97,984,000)	7,631,000
Decrease (increase) in mortgage deposits	7,893,000	1,444,000	(479,000)
Deconsolidation of previously consolidated properties	0	0	28,360,000
Acquisition of Noncontrolling Interests - Partially Owned Properties	0	(13,000)	(12,809,000)
Net cash (used for) provided by investing activities	(6,977,000)	(261,168,000)	(197,208,000)
CASH FLOWS FROM FINANCING ACTIVITIES:
Loan and bond acquisition costs	(16,526,000)	(21,209,000)	(20,421,000)
Mortgage Deposits Financing Activities	(5,631,000)	(57,000)	247,000
Mortgage notes payable:
Proceeds from Issuance of Long-term Debt	902,886,000	26,495,000	190,905,000
Restricted cash	0	2,370,000	16,596,000
Lump sum payoffs	(2,532,682,000)	(350,247,000)	(974,956,000)
Scheduled principal repayments	(12,658,000)	(14,088,000)	(16,726,000)
Notes, net:
Proceeds	1,245,550,000	0	996,190,000
Lump sum payoffs	400,000,000	975,991,000	575,641,000
Lines of credit:
Proceeds	9,832,000,000	5,876,000,000	1,455,000,000
Repayments	(9,717,000,000)	(5,876,000,000)	(1,455,000,000)
(Payments on) proceeds from settlement of derivative instruments	(44,063,000)	0	(147,306,000)
Proceeds from Employee Share Purchase Plan (ESPP)	3,401,000	5,399,000	5,262,000
Proceeds from exercise of options	17,252,000	49,039,000	95,322,000
Payments for Repurchase of Preferred Stock and Preference Stock	0	150,000,000	0
Premium on Redemption of Preferred Shares Cash	0	(23,000)	0
Payment of offering costs	(1,047,000)	(39,359,000)	(3,596,000)
Other financing activities, net	(48,000)	(48,000)	(48,000)
Contributions - Noncontrolling Interests - Partially Owned Properties	27,660,000	8,221,000	75,911,000
Contributions - Noncontrolling Interests - Operating Partnership	5,000	5,000	0
Distributions:
Net cash (used for) provided by financing activities	(1,420,995,000)	(556,318,000)	(650,746,000)
Net (decrease) increase in cash and cash equivalents	(559,056,000)	228,669,000	(47,487,000)
Cash and cash equivalents, beginning of year	612,590,000	383,921,000	431,408,000
Cash and cash equivalents, end of year	53,534,000	612,590,000	383,921,000
SUPPLEMENTAL INFORMATION:
Cash paid for interest, net of amounts capitalized	722,861,000	464,937,000	477,434,000
Net cash (received) paid for income and other taxes	1,152,000	673,000	645,000
Real estate acquisitions/dispositions/other:
Mortgage loans assumed	0	137,644,000	158,240,000
Valuation of OP Units issued	0	66,606,000	0
Amortization of deferred financing costs:
Amortization Of Deferred Financing Costs Investment In Real Estate Net	(152,000)	0	0
Amortization Of Deferred Financing Costs Deferred Financing Costs Net	22,577,000	21,435,000	17,846,000
Amortization of discounts and premiums on debt:
Mortgage notes payable	(158,625,000)	(10,333,000)	(8,260,000)
Notes, net	2,186,000	2,152,000	6,782,000
Amortization of deferred settlements on derivative instruments:
Other liabilities	(534,000)	(534,000)	(535,000)
Accumulated other comprehensive income	20,141,000	14,678,000	4,343,000
Loss From Investments In Unconsolidated Entities [Abstract]
Income Loss From Equity Method Investments Merger	53,073,000	14,000	0
Other Liabilities Loss From Investments in Unconsolidated Entities Merger	5,090,000	0	0
Unrealized loss (gain) on derivative instruments:
Other assets	(17,139,000)	7,448,000	6,826,000
Mortgage notes payable	0	(2,589,000)	(612,000)
Notes, net	(1,523,000)	(4,860,000)	(2,937,000)
Other liabilities	(39,000)	11,772,000	140,507,000
Accumulated other comprehensive (loss) income	18,771,000	(11,772,000)	(143,598,000)
Acquisition of Archstone, net of cash acquired [Abstract]
Acquisition of Archstone Investment in Real Estate Net	(8,687,355,000)	0	0
Acquisition of Archstone Investments in Unconsolidated Entities	(225,568,000)	0	0
Acquisition of Archstone Deposits Restricted	(528,000)	0	0
Acquisition of Archstone Escrow Deposits Mortgage	(37,582,000)	0	0
Acquisition of Archstone Deferred Financing Costs	(25,780,000)	0	0
Acquisition of Archstone Other Assets	(215,622,000)	0	0
Acquisition of Archstone Mortgage Notes Payable	3,076,876,000	0	0
Acquisition of Archstone Accounts Payable and Accrued Liabilities	16,984,000	0	0
Acqusition of Archstone Interest Payable	11,305,000	0	0
Acquisition of Archstone Other Liabilities	117,299,000	0	0
Acquisition of Archstone Security Deposits	10,965,000	0	0
Acquisition of Archstone Common Shares Issued	1,929,868,000	0	0
Acquisition of Archstone Noncontrolling Interests Partially Owned Properties	28,263,000	0	0
Interest capitalized for real estate and unconsolidated entities under development:
Investment in real estate, net	(45,533,000)	(21,661,000)	(8,785,000)
Investments in unconsolidated entities	(1,788,000)	(848,000)	(323,000)
Investments in unconsolidated entities [Abstract]
Investments in unconsolidated entities	(13,656,000)	(5,291,000)	(2,021,000)
Investments in unconsolidated entities other liabilities	(52,815,000)	0	0
Deconsolidation of previously consolidated properties:
Investment in real estate, net	0	0	35,495,000
Investments in unconsolidated entities	0	0	(7,135,000)
(Payments on) proceeds from settlement of derivative instruments:
Other liabilities	(44,013,000)	0	(147,306,000)
Other:
Receivable on sale of Common Shares	0	28,457,000	0
Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Gain (Loss) Arising During Period, Net of Tax	$ (613,000)	$ 0	$ 0