Fair Value Measurements (Details) (USD $)	3 Months Ended		9 Months Ended															3 Months Ended	9 Months Ended	3 Months Ended	9 Months Ended	3 Months Ended	9 Months Ended
	Sep. 30, 2011	Sep. 30, 2010	Sep. 30, 2011	Sep. 30, 2010	Dec. 31, 2010	Sep. 30, 2011 Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]	Dec. 31, 2010 Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]	Sep. 30, 2011 Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] Fair Value, Measurements, Recurring [Member]	Sep. 30, 2011 Significant Other Observable Inputs (Level 2) [Member]	Dec. 31, 2010 Significant Other Observable Inputs (Level 2) [Member]	Sep. 30, 2011 Significant Other Observable Inputs (Level 2) [Member] Fair Value, Measurements, Recurring [Member]	Sep. 30, 2011 Significant Unobservable Inputs (Level 3) [Member]	Dec. 31, 2010 Significant Unobservable Inputs (Level 3) [Member]	Sep. 30, 2011 Significant Unobservable Inputs (Level 3) [Member] Fair Value, Measurements, Recurring [Member]	Sep. 30, 2011 Total Losses [Member] Fair Value, Measurements, Recurring [Member]	Sep. 30, 2011 Fair Value, Measurements, Recurring [Member]	Dec. 31, 2010 Fair Value, Measurements, Recurring [Member]	Sep. 30, 2011 Outparcel Sale [Member]	Sep. 30, 2011 Columbia Place and Settlers Ridge Phase II Totals [Member]	Sep. 30, 2011 Columbia Place Mall [Member]	Sep. 30, 2011 Columbia Place Mall [Member]	Jun. 30, 2011 Settlers Ridge Phase II [Member]	Sep. 30, 2011 Settlers Ridge Phase II [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Liability, Number of Instruments Held	4		4
Derivative Asset, Number of Instruments Held	2		2		1
Available-for-sale Securities, Amortized Cost Basis																$ 27,186,000	$ 13,702,000
Available-for-sale Securities, Gross Unrealized Gains																6,474,000	8,410,000
Assets:
Available-for-sale securities						20,185,000	22,052,000		0	0		11,829,000	0			32,014,000	22,052,000
Privately held debt and equity securities						0	0		0	0		2,475,000	2,475,000			2,475,000	2,475,000
Interest rate cap						0	0		1,000	3,000		0	0			1,000	3,000
Long-lived assets														22,481,000	55,140,000	22,481,000
Non cash loss on impairment of long lived asset																		622,000		50,683,000		4,457,000
Real Estate Investment Property, Net Prior to Impairment Write Down																				56,746,000
Proceeds from Divestiture of Businesses																		1,477,000
Recognized realized losses on sale of marketable securities			22,000
Available-for-sale Securities, Gross Unrealized Losses																(1,646,000)	(60,000)
Interest Rate Derivative Liabilities, at Fair Value						0			5,560,000			0				5,560,000
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value																				6,063,000	6,063,000	14,873,000
Percentage of Revenue																			1.00%
Reconciliation of Carrying Amount of Real Estate Investments:
Beginning carrying value			6,890,137,000																70,668,000		58,207,000		12,461,000
Capital expenditures																			8,519,000		14,000		8,505,000
Depreciation expense																			(1,566,000)		(1,475,000)		(91,000)
Loss on impairment of real estate	51,304,000	0	55,761,000	0															(55,140,000)		(50,683,000)		(4,457,000)
Ending carrying value	$ 6,778,820,000		$ 6,778,820,000															$ 2,099,000	$ 22,481,000	$ 6,063,000	$ 6,063,000	$ 19,330,000	$ 16,418,000