Investments in Partially Owned Entities (Details) (USD $)	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012	May 09, 2013	Dec. 31, 2012	Dec. 31, 2011
Variable Interest Entity [Line Items]
Debt Instrument, Description of Variable Rate Basis	LIBOR plus 1.75%
Partially Owned Property Balance Sheet Schedule
Partially Owned Consolidated Properties	20
Partially Owned Unconsolidated Properties	1
Partially Owned Consolidated Units	3,917
Partially Owned Unconsolidated Units	336
ASSETS
Real Estate Investment Property, at Cost	$ 27,364,093,000			$ 21,008,429,000
Real Estate Investment Property, Accumulated Depreciation	(4,434,775,000)			(4,912,221,000)
Investment in real estate, net	22,929,318,000			16,096,208,000
Cash and Cash Equivalents, at Carrying Value	56,087,000	219,628,000		612,590,000	383,921,000
Investments in and Advance to Affiliates, Subsidiaries, Associates, and Joint Ventures	193,338,000			17,877,000
Restricted Cash and Cash Equivalents	147,515,000			250,442,000
Deferred Finance Costs, Net	71,229,000			44,382,000
Other Assets	358,136,000			170,372,000
Total assets	23,795,158,000			17,201,000,000
LIABILITIES AND EQUITY
Secured Debt	6,380,424,000			3,898,369,000
Accounts Payable And Accrued Liabilities Current And Noncurrent Other Than Interest And Dividend Payable	104,836,000			38,372,000
Interest Payable	88,518,000			76,223,000
Other Liabilities	401,225,000			304,518,000
Security Deposit Liability	72,669,000			66,988,000
Total liabilities	12,973,313,000			9,275,521,000
Noncontrolling Interests Partially Owned Properties	105,930,000			77,688,000
Total liabilities and equity	23,795,158,000			17,201,000,000
Partially Owned Property Income Statement Schedule
Operating revenue	539,162,000	446,448,000
Depreciation	205,272,000	148,246,000
General and Administrative Expense	16,496,000	13,688,000
Operating Income (Loss)	117,529,000	114,476,000
Interest and Other Income	256,000	169,000
Interest:
Interest Expense, Debt	195,685,000	118,011,000
Amortization of Financing Costs	7,023,000	2,934,000
Income before income and other taxes, net gain on sales of land parcels and discontinued operations	(106,579,000)	(13,256,000)
Income and other tax (expense) benefit	(407,000)	(170,000)
Income (Loss) from Equity Method Investments	(355,000)	0
Discontinued Operation, Gain (Loss) on Disposal of Discontinued Operation, Net of Tax	1,198,922,000	132,956,000
Net income	1,061,034,000	152,167,000
Investments In Partially Owned Entities (Textuals) [Abstract]
Liquidation Value Preferred Interests			65,000,000.00
Joint Venture Partner Ownership Percentage	80.00%
Equity Method Investment, Ownership Percentage	20.00%
Variable Interest Entity, Consolidated, Carrying Amount, Assets	5,000,000
Project Cost	232,800,000
Debt Instrument, Maturity Date	Sep. 01, 2014
Land purchase price	76,100,000
Investment in Joint Venture	212,700,000
Number of Joint Ventures	2
Partners Payments To Acquire Equity Method Investments	40,100,000
Number of joint venture loans	2
Consolidated Development Projects Held for and or Under Development [Member]
Partially Owned Property Balance Sheet Schedule
Partially Owned Consolidated Properties	0
Partially Owned Consolidated Units	0
ASSETS
Real Estate Investment Property, at Cost	219,252,000
Real Estate Investment Property, Accumulated Depreciation	0
Investment in real estate, net	219,252,000
Cash and Cash Equivalents, at Carrying Value	4,022,000
Investments in and Advance to Affiliates, Subsidiaries, Associates, and Joint Ventures	0
Restricted Cash and Cash Equivalents	43,616,000
Deferred Finance Costs, Net	0
Other Assets	5,781,000
Total assets	272,671,000
LIABILITIES AND EQUITY
Secured Debt	0
Accounts Payable And Accrued Liabilities Current And Noncurrent Other Than Interest And Dividend Payable	1,788,000
Interest Payable	0
Other Liabilities	1,224,000
Security Deposit Liability	0
Total liabilities	3,012,000
Noncontrolling Interests Partially Owned Properties	89,888,000
Parent Equity Interest	179,771,000
Total Equity Interest	269,659,000
Total liabilities and equity	272,671,000
Debt-Secured:
Debt Ownership	0
Noncontrolling Ownership	0
Partially Owned Property Income Statement Schedule
Operating revenue	0
Operating Expenses	52,000
Gross Profit	(52,000)
Depreciation	0
General and Administrative Expense	122,000
Operating Income (Loss)	(174,000)
Interest and Other Income	1,000
Other Nonoperating Income (Expense)	(86,000)
Interest:
Interest Expense, Debt	0
Amortization of Financing Costs	0
Income before income and other taxes, net gain on sales of land parcels and discontinued operations	(259,000)
Income and other tax (expense) benefit	(11,000)
Income (Loss) from Equity Method Investments	0
Discontinued Operation, Gain (Loss) on Disposal of Discontinued Operation, Net of Tax	0
Net income	(270,000)
Consolidated Operating [Domain]
Partially Owned Property Balance Sheet Schedule
Partially Owned Consolidated Properties	20
Partially Owned Consolidated Units	3,917
ASSETS
Real Estate Investment Property, at Cost	644,208,000
Real Estate Investment Property, Accumulated Depreciation	(160,227,000)
Investment in real estate, net	483,981,000
Cash and Cash Equivalents, at Carrying Value	12,437,000
Investments in and Advance to Affiliates, Subsidiaries, Associates, and Joint Ventures	56,253,000
Restricted Cash and Cash Equivalents	24,582,000
Deferred Finance Costs, Net	2,632,000
Other Assets	26,700,000
Total assets	606,585,000
LIABILITIES AND EQUITY
Secured Debt	343,218,000
Accounts Payable And Accrued Liabilities Current And Noncurrent Other Than Interest And Dividend Payable	2,201,000
Interest Payable	1,195,000
Other Liabilities	1,168,000
Security Deposit Liability	1,765,000
Total liabilities	349,547,000
Noncontrolling Interests Partially Owned Properties	16,042,000
Parent Equity Interest	240,996,000
Total Equity Interest	257,038,000
Total liabilities and equity	606,585,000
Debt-Secured:
Debt Ownership	266,228,000
Noncontrolling Ownership	76,990,000
Partially Owned Property Income Statement Schedule
Operating revenue	17,485,000
Operating Expenses	5,602,000
Gross Profit	11,883,000
Depreciation	6,094,000
General and Administrative Expense	13,000
Operating Income (Loss)	5,776,000
Interest and Other Income	3,000
Other Nonoperating Income (Expense)	0
Interest:
Interest Expense, Debt	(2,854,000)
Amortization of Financing Costs	(50,000)
Income before income and other taxes, net gain on sales of land parcels and discontinued operations	2,875,000
Income and other tax (expense) benefit	(39,000)
Income (Loss) from Equity Method Investments	(97,000)
Discontinued Operation, Gain (Loss) on Disposal of Discontinued Operation, Net of Tax	2,807,000
Net income	5,546,000
Consolidated Total [Domain]
Partially Owned Property Balance Sheet Schedule
Partially Owned Consolidated Properties	20
Partially Owned Consolidated Units	3,917
ASSETS
Real Estate Investment Property, at Cost	863,460,000
Real Estate Investment Property, Accumulated Depreciation	(160,227,000)
Investment in real estate, net	703,233,000
Cash and Cash Equivalents, at Carrying Value	16,459,000
Investments in and Advance to Affiliates, Subsidiaries, Associates, and Joint Ventures	56,253,000
Restricted Cash and Cash Equivalents	68,198,000
Deferred Finance Costs, Net	2,632,000
Other Assets	32,481,000
Total assets	879,256,000
LIABILITIES AND EQUITY
Secured Debt	343,218,000
Accounts Payable And Accrued Liabilities Current And Noncurrent Other Than Interest And Dividend Payable	3,989,000
Interest Payable	1,195,000
Other Liabilities	2,392,000
Security Deposit Liability	1,765,000
Total liabilities	352,559,000
Noncontrolling Interests Partially Owned Properties	105,930,000
Parent Equity Interest	420,767,000
Total Equity Interest	526,697,000
Total liabilities and equity	879,256,000
Debt-Secured:
Debt Ownership	266,228,000
Noncontrolling Ownership	76,990,000
Partially Owned Property Income Statement Schedule
Operating revenue	17,485,000
Operating Expenses	5,654,000
Gross Profit	11,831,000
Depreciation	6,094,000
General and Administrative Expense	135,000
Operating Income (Loss)	5,602,000
Interest and Other Income	4,000
Other Nonoperating Income (Expense)	(86,000)
Interest:
Interest Expense, Debt	(2,854,000)
Amortization of Financing Costs	(50,000)
Income before income and other taxes, net gain on sales of land parcels and discontinued operations	2,616,000
Income and other tax (expense) benefit	(50,000)
Income (Loss) from Equity Method Investments	(97,000)
Discontinued Operation, Gain (Loss) on Disposal of Discontinued Operation, Net of Tax	2,807,000
Net income	5,276,000
Unconsolidated Development Projects Held for and or Under Development [Domain]
Partially Owned Property Balance Sheet Schedule
Partially Owned Unconsolidated Properties	0
Partially Owned Unconsolidated Units	0
ASSETS
Real Estate Investment Property, at Cost	280,326,000
Real Estate Investment Property, Accumulated Depreciation	0
Investment in real estate, net	280,326,000
Cash and Cash Equivalents, at Carrying Value	2,607,000
Investments in and Advance to Affiliates, Subsidiaries, Associates, and Joint Ventures	0
Restricted Cash and Cash Equivalents	0
Deferred Finance Costs, Net	57,000
Other Assets	346,000
Total assets	283,336,000
LIABILITIES AND EQUITY
Secured Debt	117,688,000
Accounts Payable And Accrued Liabilities Current And Noncurrent Other Than Interest And Dividend Payable	10,127,000
Interest Payable	460,000
Other Liabilities	242,000
Security Deposit Liability	47,000
Total liabilities	128,564,000
Noncontrolling Interests Partially Owned Properties	114,909,000
Parent Equity Interest	39,863,000
Total Equity Interest	154,772,000
Total liabilities and equity	283,336,000
Debt-Secured:
Debt Ownership	39,120,000
Noncontrolling Ownership	78,568,000
Partially Owned Property Income Statement Schedule
Operating revenue	219,000
Operating Expenses	256,000
Gross Profit	(37,000)
Depreciation	0
General and Administrative Expense	0
Operating Income (Loss)	(37,000)
Interest and Other Income	0
Other Nonoperating Income (Expense)	0
Interest:
Interest Expense, Debt	(16,000)
Amortization of Financing Costs	0
Income before income and other taxes, net gain on sales of land parcels and discontinued operations	(53,000)
Income and other tax (expense) benefit	0
Income (Loss) from Equity Method Investments	0
Discontinued Operation, Gain (Loss) on Disposal of Discontinued Operation, Net of Tax	0
Net income	(53,000)
Unconsolidated Operating [Domain]
Partially Owned Property Balance Sheet Schedule
Partially Owned Unconsolidated Properties	1
Partially Owned Unconsolidated Units	336
ASSETS
Real Estate Investment Property, at Cost	55,017,000
Real Estate Investment Property, Accumulated Depreciation	(540,000)
Investment in real estate, net	54,477,000
Cash and Cash Equivalents, at Carrying Value	1,589,000
Investments in and Advance to Affiliates, Subsidiaries, Associates, and Joint Ventures	0
Restricted Cash and Cash Equivalents	0
Deferred Finance Costs, Net	0
Other Assets	1,336,000
Total assets	57,402,000
LIABILITIES AND EQUITY
Secured Debt	30,550,000
Accounts Payable And Accrued Liabilities Current And Noncurrent Other Than Interest And Dividend Payable	0
Interest Payable	0
Other Liabilities	1,681,000
Security Deposit Liability	0
Total liabilities	32,231,000
Noncontrolling Interests Partially Owned Properties	20,137,000
Parent Equity Interest	5,034,000
Total Equity Interest	25,171,000
Total liabilities and equity	57,402,000
Debt-Secured:
Debt Ownership	6,110,000
Noncontrolling Ownership	24,440,000
Partially Owned Property Income Statement Schedule
Operating revenue	453,000
Operating Expenses	185,000
Gross Profit	268,000
Depreciation	540,000
General and Administrative Expense	0
Operating Income (Loss)	(272,000)
Interest and Other Income	0
Other Nonoperating Income (Expense)	(49,000)
Interest:
Interest Expense, Debt	(87,000)
Amortization of Financing Costs	0
Income before income and other taxes, net gain on sales of land parcels and discontinued operations	(408,000)
Income and other tax (expense) benefit	0
Income (Loss) from Equity Method Investments	0
Discontinued Operation, Gain (Loss) on Disposal of Discontinued Operation, Net of Tax	0
Net income	(408,000)
Unconsolidated Total [Domain]
Partially Owned Property Balance Sheet Schedule
Partially Owned Unconsolidated Properties	1
Partially Owned Unconsolidated Units	336
ASSETS
Real Estate Investment Property, at Cost	335,343,000
Real Estate Investment Property, Accumulated Depreciation	(540,000)
Investment in real estate, net	334,803,000
Cash and Cash Equivalents, at Carrying Value	4,196,000
Investments in and Advance to Affiliates, Subsidiaries, Associates, and Joint Ventures	0
Restricted Cash and Cash Equivalents	0
Deferred Finance Costs, Net	57,000
Other Assets	1,682,000
Total assets	340,738,000
LIABILITIES AND EQUITY
Secured Debt	148,238,000
Accounts Payable And Accrued Liabilities Current And Noncurrent Other Than Interest And Dividend Payable	10,127,000
Interest Payable	460,000
Other Liabilities	1,923,000
Security Deposit Liability	47,000
Total liabilities	160,795,000
Noncontrolling Interests Partially Owned Properties	135,046,000
Parent Equity Interest	44,897,000
Total Equity Interest	179,943,000
Total liabilities and equity	340,738,000
Debt-Secured:
Debt Ownership	45,230,000
Noncontrolling Ownership	103,008,000
Partially Owned Property Income Statement Schedule
Operating revenue	672,000
Operating Expenses	441,000
Gross Profit	231,000
Depreciation	540,000
General and Administrative Expense	0
Operating Income (Loss)	(309,000)
Interest and Other Income	0
Other Nonoperating Income (Expense)	(49,000)
Interest:
Interest Expense, Debt	(103,000)
Amortization of Financing Costs	0
Income before income and other taxes, net gain on sales of land parcels and discontinued operations	(461,000)
Income and other tax (expense) benefit	0
Income (Loss) from Equity Method Investments	0
Discontinued Operation, Gain (Loss) on Disposal of Discontinued Operation, Net of Tax	0
Net income	(461,000)
Residual JV [Domain]
ASSETS
Investments in and Advance to Affiliates, Subsidiaries, Associates, and Joint Ventures	105,200,000
Joint Venture Partner [Member]
LIABILITIES AND EQUITY
Noncontrolling Interests Partially Owned Properties	87,300,000
Investments In Partially Owned Entities (Textuals) [Abstract]
Land purchase price	57,900,000
Business Acquisition, Cost of Acquired Entity, Purchase Price	75,700,000
Company's Portion [Member]
Investments In Partially Owned Entities (Textuals) [Abstract]
Business Acquisition, Cost of Acquired Entity, Purchase Price	102,500,000
Nexus Sawgrass [Member]
LIABILITIES AND EQUITY
Secured Debt	36,300,000
Investments In Partially Owned Entities (Textuals) [Abstract]
Maximum Debt Commitment	48,700,000
Debt Instrument, Interest Rate, Stated Percentage	5.60%
Debt Instrument, Maturity Date	Jan. 01, 2021
Domain [Member]
LIABILITIES AND EQUITY
Secured Debt	57,400,000
Investments In Partially Owned Entities (Textuals) [Abstract]
Maximum Debt Commitment	98,600,000
Debt Instrument, Interest Rate, Stated Percentage	5.75%
Debt Instrument, Maturity Date	Jan. 01, 2022
Archstone Transaction [Member]
Investments In Partially Owned Entities (Textuals) [Abstract]
Liquidation Value Preferred Interests	167,200,000.00
Business Acquisition, Percentage of Voting Interests Acquired	60.00%		60.00%
Joint Venture Partner Ownership Percentage	40.00%
Enclave at Wellington [Domain]
Investments In Partially Owned Entities (Textuals) [Abstract]
Business Acquisition, Percentage of Voting Interests Acquired	95.00%
Partially Owned Consolidated Properties	268
Initial Basis of Land, Consolidated	26,200,000
Project Cost	50,000,000
East Palmetto Park [Domain]
Investments In Partially Owned Entities (Textuals) [Abstract]
Business Acquisition, Percentage of Voting Interests Acquired	90.00%
Partially Owned Consolidated Properties	377
Initial Basis of Land, Consolidated	20,200,000
Wisconsin Place [Domain]
ASSETS
Investments in and Advance to Affiliates, Subsidiaries, Associates, and Joint Ventures	56,500,000
Investments In Partially Owned Entities (Textuals) [Abstract]
Business Acquisition, Percentage of Voting Interests Acquired	75.00%
Partially Owned Consolidated Properties	432
Initial Basis of Land, Consolidated	189,400,000
San Norterra [Domain]
Variable Interest Entity [Line Items]
Debt Instrument, Description of Variable Rate Basis	LIBOR plus 2.25%
LIABILITIES AND EQUITY
Secured Debt	24,000,000
Investments In Partially Owned Entities (Textuals) [Abstract]
Equity Method Investment, Ownership Percentage	85.00%
Project Cost	56,300,000
Partially Owned Unconsolidated Units To Be Developed	388
Initial Basis of Land, Unconsolidated	16,900,000
Maximum Debt Commitment	34,800,000
Debt Instrument, Maturity Date	Jan. 06, 2015
Waterton Tenside [Domain]
Partially Owned Property Balance Sheet Schedule
Partially Owned Unconsolidated Units	336
LIABILITIES AND EQUITY
Secured Debt	30,600,000
Investments In Partially Owned Entities (Textuals) [Abstract]
Equity Method Investment, Ownership Percentage	20.00%
Initial Basis of Land, Unconsolidated	5,100,000
Debt Instrument, Interest Rate, Stated Percentage	3.66%
Debt Instrument, Maturity Date	Dec. 01, 2018
Mission Gorge [Domain]
Investments In Partially Owned Entities (Textuals) [Abstract]
Equity Method Investment, Ownership Percentage	23.17%
Partially Owned Unconsolidated Units To Be Developed	444
Initial Basis of Land, Unconsolidated	4,100,000
Parkside at Emeryville [Domain]
Variable Interest Entity [Line Items]
Debt Instrument, Description of Variable Rate Basis	LIBOR plus 2.25%
Investments In Partially Owned Entities (Textuals) [Abstract]
Equity Method Investment, Ownership Percentage	5.00%
Project Cost	75,000,000
Partially Owned Unconsolidated Units To Be Developed	180
Initial Basis of Land, Unconsolidated	1,400,000
Maximum Debt Commitment	39,500,000
Debt Instrument, Maturity Date	Aug. 14, 2015
Unconsolidated Project Under Development Commitment Fund	$ 19,700,000
Minimum [Member]
Variable Interest Entity [Line Items]
Debt Instrument, Description of Variable Rate Basis	SIFMA plus 0.860%