Investments in Partially Owned Entities (Details) - USD ($)	3 Months Ended		9 Months Ended		31 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Dec. 31, 2014	Dec. 31, 2013	Feb. 27, 2013
Partially Owned Property Balance Sheet Schedule
Number of Real Estate Properties	392		392		392
Number of Units in Real Estate Property	109,347		109,347		109,347
ASSETS
Investment in real estate	$ 28,159,481,000		$ 28,159,481,000		$ 28,159,481,000	$ 27,675,383,000
Accumulated depreciation	(5,914,695,000)		(5,914,695,000)		(5,914,695,000)	(5,432,805,000)
Investment in real estate, net	22,244,786,000		22,244,786,000		22,244,786,000	22,242,578,000
Cash and cash equivalents	37,366,000	$ 31,478,000	37,366,000	$ 31,478,000	37,366,000	40,080,000	$ 53,534,000
Investments in unconsolidated entities	74,108,000		74,108,000		74,108,000	105,434,000
Deposits – restricted	135,674,000		135,674,000		135,674,000	72,303,000
Deferred financing costs, net	57,001,000		57,001,000		57,001,000	58,380,000
Other assets	405,798,000		405,798,000		405,798,000	383,754,000
Total assets	23,008,804,000		23,008,804,000		23,008,804,000	22,950,614,000
LIABILITIES AND EQUITY
Secured Debt	4,891,529,000		4,891,529,000		4,891,529,000	5,086,515,000
Accounts payable & accrued expenses	253,027,000		253,027,000		253,027,000	153,590,000
Accrued interest payable	86,083,000		86,083,000		86,083,000	89,540,000
Other Liabilities	353,106,000		353,106,000		353,106,000	389,915,000
Security deposits	76,934,000		76,934,000		76,934,000	75,633,000
Total liabilities	11,781,555,000		11,781,555,000		11,781,555,000	11,742,105,000
Noncontrolling Interests – Partially Owned Properties/Partners' equity	4,643,000		4,643,000		4,643,000	124,909,000
Liabilities and Equity	23,008,804,000		23,008,804,000		23,008,804,000	22,950,614,000
Partially Owned Property Income Statement Schedule
Operating revenue	696,289,000	664,078,000	2,041,772,000	1,950,088,000
Depreciation	196,059,000	190,469,000	584,862,000	565,772,000
General and administrative/other	15,290,000	9,968,000	50,942,000	41,296,000
Operating income	257,501,000	243,274,000	721,856,000	670,843,000
Interest and other income	256,000	576,000	6,906,000	3,213,000
Interest:
Expense incurred, net	(114,205,000)	(118,251,000)	(333,622,000)	(347,224,000)
Amortization of deferred financing costs	(2,607,000)	(2,628,000)	(7,734,000)	(8,554,000)
Income before income and other taxes, income (loss) from investments in unconsolidated entities, net gain (loss) on sales of real estate properties and land parcels and discontinued operations	139,806,000	117,995,000	384,567,000	311,099,000
Income and other tax (expense) benefit	(329,000)	(260,000)	(698,000)	(1,146,000)
Income (loss) from investments in unconsolidated entities	(1,041,000)	(1,176,000)	14,388,000	(10,201,000)
Net income	205,456,000	$ 231,190,000	694,298,000	431,642,000
Investments In Partially Owned Entities (Textuals) [Abstract]
Noncontrolling Interests – Partially Owned Properties/Partners' equity	4,643,000		4,643,000		4,643,000	124,909,000
Investments in unconsolidated entities	74,108,000		74,108,000		74,108,000	105,434,000
Secured Debt	$ 4,891,529,000		4,891,529,000		$ 4,891,529,000	$ 5,086,515,000
Distributions from unconsolidated entities – return of capital			$ 45,245,000	$ 77,042,000
Consolidated Properties [Member]
Partially Owned Property Balance Sheet Schedule
Number of Real Estate Properties	19		19		19
Number of Units in Real Estate Property	3,771		3,771		3,771
ASSETS
Investment in real estate	$ 687,814,000		$ 687,814,000		$ 687,814,000
Accumulated depreciation	(211,120,000)		(211,120,000)		(211,120,000)
Investment in real estate, net	476,694,000		476,694,000		476,694,000
Cash and cash equivalents	19,242,000		19,242,000		19,242,000
Investments in unconsolidated entities	50,140,000		50,140,000		50,140,000
Deposits – restricted	335,000		335,000		335,000
Deferred financing costs, net	1,875,000		1,875,000		1,875,000
Other assets	26,816,000		26,816,000		26,816,000
Total assets	575,102,000		575,102,000		575,102,000
LIABILITIES AND EQUITY
Secured Debt	343,341,000		343,341,000		343,341,000
Accounts payable & accrued expenses	3,318,000		3,318,000		3,318,000
Accrued interest payable	1,206,000		1,206,000		1,206,000
Other Liabilities	709,000		709,000		709,000
Security deposits	2,017,000		2,017,000		2,017,000
Total liabilities	350,591,000		350,591,000		350,591,000
Noncontrolling Interests – Partially Owned Properties/Partners' equity	4,643,000		4,643,000		4,643,000
Company equity/General and Limited Partners' Capital	219,868,000		219,868,000		219,868,000
Total equity/capital	224,511,000		224,511,000		224,511,000
Liabilities and Equity	575,102,000		575,102,000		575,102,000
Partially Owned Property Income Statement Schedule
Operating revenue			70,142,000
Operating expenses			20,208,000
Net operating income			49,934,000
Depreciation			16,638,000
General and administrative/other			44,000
Operating income			33,252,000
Interest and other income			8,000
Other expenses			(50,000)
Interest:
Expense incurred, net			(11,704,000)
Amortization of deferred financing costs			(266,000)
Income before income and other taxes, income (loss) from investments in unconsolidated entities, net gain (loss) on sales of real estate properties and land parcels and discontinued operations			21,240,000
Income and other tax (expense) benefit			(35,000)
Income (loss) from investments in unconsolidated entities			(1,104,000)
Net income			20,101,000
Investments In Partially Owned Entities (Textuals) [Abstract]
Noncontrolling Interests – Partially Owned Properties/Partners' equity	4,643,000		4,643,000		4,643,000
Investments in unconsolidated entities	50,140,000		50,140,000		50,140,000
Secured Debt	$ 343,341,000		$ 343,341,000		$ 343,341,000
Unconsolidated Properties [Member]
Partially Owned Property Balance Sheet Schedule
Number of Real Estate Properties	3		3		3
Number of Units in Real Estate Property	1,281		1,281		1,281
ASSETS
Investment in real estate	$ 290,733,000		$ 290,733,000		$ 290,733,000
Accumulated depreciation	(27,563,000)		(27,563,000)		(27,563,000)
Investment in real estate, net	263,170,000		263,170,000		263,170,000
Cash and cash equivalents	8,912,000		8,912,000		8,912,000
Investments in unconsolidated entities	0		0		0
Deposits – restricted	284,000		284,000		284,000
Deferred financing costs, net	6,000		6,000		6,000
Other assets	882,000		882,000		882,000
Total assets	273,254,000		273,254,000		273,254,000
LIABILITIES AND EQUITY
Secured Debt	174,992,000		174,992,000		174,992,000
Accounts payable & accrued expenses	3,227,000		3,227,000		3,227,000
Accrued interest payable	691,000		691,000		691,000
Other Liabilities	513,000		513,000		513,000
Security deposits	614,000		614,000		614,000
Total liabilities	180,037,000		180,037,000		180,037,000
Noncontrolling Interests – Partially Owned Properties/Partners' equity	90,878,000		90,878,000		90,878,000
Company equity/General and Limited Partners' Capital	2,339,000		2,339,000		2,339,000
Total equity/capital	93,217,000		93,217,000		93,217,000
Liabilities and Equity	273,254,000		273,254,000		273,254,000
Partially Owned Property Income Statement Schedule
Operating revenue			24,125,000
Operating expenses			8,949,000
Net operating income			15,176,000
Depreciation			9,251,000
General and administrative/other			178,000
Operating income			5,747,000
Interest and other income			2,000
Other expenses			0
Interest:
Expense incurred, net			(7,047,000)
Amortization of deferred financing costs			(1,000)
Income before income and other taxes, income (loss) from investments in unconsolidated entities, net gain (loss) on sales of real estate properties and land parcels and discontinued operations			(1,299,000)
Income and other tax (expense) benefit			(18,000)
Income (loss) from investments in unconsolidated entities			0
Net income			(1,317,000)
Investments In Partially Owned Entities (Textuals) [Abstract]
Noncontrolling Interests – Partially Owned Properties/Partners' equity	90,878,000		90,878,000		90,878,000
Investments in unconsolidated entities	0		0		0
Secured Debt	174,992,000		174,992,000		174,992,000
Residual JV [Domain]
ASSETS
Investments in unconsolidated entities	$ 4,500,000		$ 4,500,000		$ 4,500,000			$ 147,600,000
Investments In Partially Owned Entities (Textuals) [Abstract]
Business Acquisition, Percentage of Voting Interests Acquired	60.00%		60.00%		60.00%
Joint Venture Partner Ownership Percentage	40.00%		40.00%		40.00%
Investments in unconsolidated entities	$ 4,500,000		$ 4,500,000		$ 4,500,000			$ 147,600,000
Distributions from unconsolidated entities – return of capital			45,100,000
Residual JV [Domain] | Settled Litigation [Member]
Investments In Partially Owned Entities (Textuals) [Abstract]
Distributions from unconsolidated entities – return of capital			16,800,000
Residual JV [Domain] | Property, Plant and Equipment [Member]
Investments In Partially Owned Entities (Textuals) [Abstract]
Distributions from unconsolidated entities – return of capital			24,800,000
Legacy JV [Domain]
Investments In Partially Owned Entities (Textuals) [Abstract]
Liquidation Value Preferred Interests	$ 42,800,000		$ 42,800,000		$ 42,800,000
Business Acquisition, Percentage of Voting Interests Acquired	60.00%		60.00%		60.00%
Joint Venture Partner Ownership Percentage	40.00%		40.00%		40.00%
Distribution Made to Limited Liability Company (LLC) Member, Cash Distributions Paid			$ 27,900,000
Wisconsin Place [Domain]
Partially Owned Property Balance Sheet Schedule
Number of Units in Real Estate Property	432		432		432
ASSETS
Investments in unconsolidated entities	$ 50,100,000		$ 50,100,000		$ 50,100,000
Investments In Partially Owned Entities (Textuals) [Abstract]
Business Acquisition, Percentage of Voting Interests Acquired	75.00%		75.00%		75.00%
Investments in unconsolidated entities	$ 50,100,000		$ 50,100,000		$ 50,100,000
Basis of joint venture	$ 176,800,000		$ 176,800,000		$ 176,800,000
Waterton Tenside [Domain]
Partially Owned Property Balance Sheet Schedule
Number of Units in Real Estate Property	336		336		336
ASSETS
Investments in unconsolidated entities	$ 4,000,000		$ 4,000,000		$ 4,000,000
LIABILITIES AND EQUITY
Secured Debt	29,600,000		29,600,000		29,600,000
Investments In Partially Owned Entities (Textuals) [Abstract]
Investments in unconsolidated entities	$ 4,000,000		$ 4,000,000		$ 4,000,000
Equity Method Investment, Ownership Percentage	20.00%		20.00%		20.00%
Secured Debt	$ 29,600,000		$ 29,600,000		$ 29,600,000
Debt Instrument, Interest Rate, Stated Percentage	3.66%		3.66%		3.66%
Debt Instrument, Maturity Date			Dec. 01, 2018
Nexus Sawgrass [Member]
Partially Owned Property Balance Sheet Schedule
Number of Units in Real Estate Property	501		501		501
ASSETS
Investments in unconsolidated entities	$ 5,300,000		$ 5,300,000		$ 5,300,000
LIABILITIES AND EQUITY
Secured Debt	48,600,000		48,600,000		48,600,000
Investments In Partially Owned Entities (Textuals) [Abstract]
Investments in unconsolidated entities	$ 5,300,000		$ 5,300,000		$ 5,300,000
Equity Method Investment, Ownership Percentage	20.00%		20.00%		20.00%
Secured Debt	$ 48,600,000		$ 48,600,000		$ 48,600,000
Debt Instrument, Interest Rate, Stated Percentage	5.60%		5.60%		5.60%
Debt Instrument, Maturity Date			Jan. 01, 2021
Domain [Member]
Partially Owned Property Balance Sheet Schedule
Number of Units in Real Estate Property	444		444		444
ASSETS
Investments in unconsolidated entities	$ 10,200,000		$ 10,200,000		$ 10,200,000
LIABILITIES AND EQUITY
Secured Debt	96,800,000		96,800,000		96,800,000
Investments In Partially Owned Entities (Textuals) [Abstract]
Investments in unconsolidated entities	$ 10,200,000		$ 10,200,000		$ 10,200,000
Equity Method Investment, Ownership Percentage	20.00%		20.00%		20.00%
Secured Debt	$ 96,800,000		$ 96,800,000		$ 96,800,000
Debt Instrument, Interest Rate, Stated Percentage	5.75%		5.75%		5.75%
Debt Instrument, Maturity Date			Jan. 01, 2022
Germany [Domain]
Investments In Partially Owned Entities (Textuals) [Abstract]
Distributions from unconsolidated entities – return of capital			$ 3,500,000		$ 102,000,000
Company's Portion [Member] | Legacy JV [Domain]
Investments In Partially Owned Entities (Textuals) [Abstract]
Distribution Made to Limited Liability Company (LLC) Member, Cash Distributions Paid			$ 16,700,000