Discontinued Operations (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2012		Mar. 31, 2011	Dec. 31, 2011
Discontinued Operations and Disposal Groups [Abstract]
Rental and other revenues	$ 429		$ 1,241
Operating expenses:
Rental property and other expenses	193		445
Depreciation and amortization	153		256
Total operating expenses	346		701
Income from discontinued operations	83		540
Net gains on disposition of discontinued operations	5,134		0
Total discontinued operations	5,217		540
Assets:
Land	802			1,901
Buildings and tenant improvements	9,444			16,184
Less accumulated depreciation	(3,292)			(5,523)
Net real estate assets	6,954			12,562
Accrued straight line rents receivable	393			399
Deferred leasing costs, net	205			195
Prepaid expenses and other assets	4			104
Real estate and other assets, net, held for sale	7,556			13,260
Tenant security deposits, deferred rents and accrued costs	$ 81	[1]		$ 72	[1]

[1] Included in accounts payable, accrued expenses and other liabilities.