Discontinued Operations (Details) (USD $)	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2011 Sqft	Jun. 30, 2010 Sqft	Jun. 30, 2011 Sqft	Jun. 30, 2010 Sqft	Dec. 31, 2010 Sqft	Dec. 31, 2009
Balance sheet relating to asset held for sale
Land	$ 12,300		$ 12,300
Building	865,800		865,800
Fixtures and tenant improvements	43,600		43,600
Total land and building	921,700		921,700
Less: Accumulated depreciation	(727,100)		(727,100)
Total assets held for sale	194,600		194,600
Operating results relating to assets sold or designated as held for sale
Revenues	1,057,000	5,875,000	3,184,000	12,702,000
Expenses:
Operating expenses	308,000	3,940,000	999,000	8,208,000
Impairment charges	1,904,000	57,920,000	3,887,000	60,993,000
Interest, net	327,000	4,005,000	878,000	8,400,000
Depreciation and amortization	378,000	2,381,000	1,032,000	4,985,000
Total expenses	2,917,000	68,246,000	6,796,000	82,586,000
Loss from discontinued operations	(1,860,000)	(62,371,000)	(3,612,000)	(69,884,000)
Loss on disposition of real estate	(7,264,000)	(4,057,000)	(7,020,000)	(3,491,000)
Net loss	$ (9,124,000)	$ (66,428,000)	$ (10,632,000)	$ (73,375,000)
Discontinued Operations (Textuals) [Abstract]
Number of assets held for sale	1		1
Number of properties sold	12	31	12	31
Number of properties held for sale	1	0	1	0		2
Properties aggregate square feet	800,000	2,900,000	800,000	2,900,000
Other properties deconsolidated for accounting purpose		25		25	25
Properties aggregate square feet of deconsolidated joint venture		1,900,000		1,900,000	1,900,000