Discontinued Operations (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		12 Months Ended
	Mar. 31, 2012 Property	Mar. 31, 2011	Dec. 31, 2011 Property
Balance sheet relating to asset held for sale
Land	$ 2,549
Buildings	22,577
Fixtures and tenant improvements	3,211
Land held for development and construction in progress	22
Carrying amount of real estate assets held for sale	28,359
Less: Accumulated depreciation	(20,334)
Total assets held for sale	8,025		2,290
Operating results relating to assets sold or designated as held for sale
Revenues	1,370	11,039
Expenses:
Operating expenses	735	4,329
Impairment charges	3,854	1,983
Interest, net	142	3,039
Depreciation and amortization	289	3,017
Total expenses	5,020	12,368
Loss before disposition of real estate	(3,650)	(1,329)
Gain on disposition of real estate, net of tax	70	244
Loss from discontinued operations	$ (3,580)	$ (1,085)
Discontinued Operations and Disposition of Real Estate and Real Estate Investments (Textual) [Abstract]
Number of properties sold	6		34
Number of assets held for sale	4