Consolidated Statements of Equity (Parenthetical) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013	Mar. 31, 2014 Series D Preferred Shares of Beneficial Interest [Member]	Mar. 31, 2013 Series D Preferred Shares of Beneficial Interest [Member]	Mar. 31, 2014 Accumulated Distributions in Excess of Net Income [Member]	Mar. 31, 2013 Accumulated Distributions in Excess of Net Income [Member]	Mar. 31, 2014 Accumulated Distributions in Excess of Net Income [Member] Series D Preferred Shares of Beneficial Interest [Member]	Mar. 31, 2013 Accumulated Distributions in Excess of Net Income [Member] Series D Preferred Shares of Beneficial Interest [Member]
Dividends declared on Common Shares of Beneficial Interest	$ 0.1625	$ 0.1625			$ 0.1625	$ 0.1625
Dividends declared on Series D Preferred Shares			$ 0.578125	$ 0.578125			$ 0.578125	$ 0.578125