Subsequent Events (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012	Mar. 31, 2013 Declaration of Dividends [Member]	Mar. 31, 2013 Declaration of Dividends [Member] Common Stock [Member]	Mar. 31, 2013 Declaration of Dividends [Member] Series J Preferred Stock [Member]	Mar. 31, 2013 Declaration of Dividends [Member] Series K Preferred Stock [Member]	Mar. 31, 2013 Declaration of Dividends [Member] Series L Preferred Stock [Member]	Jun. 30, 2013 Retail Property Sale [Member] sqft
Subsequent Event [Line Items]
Square Footage Of Real Estate Properties Acquired Or Disposed								391,000
Proceeds from land and depreciated property sales, net	$ 61,931	$ 63,281						$ 184,500
Common stock dividends declared per share				$ 0.17
Preferred stock dividends declared per share					$ 0.414063	$ 0.406250	$ 0.412500
Record date				May 16, 2013	May 16, 2013	May 16, 2013	May 16, 2013
Payment date				May 31, 2013	May 31, 2013	May 31, 2013	May 31, 2013
Declared date			Apr. 24, 2013
Earnings from land and depreciated property sales	$ (9,122)	$ (6,199)						$ 80,000