Preferred Shares of Beneficial Interest (Preferred Dividends Declared Per Share) (Details)	12 Months Ended
Dec. 31, 2015 $ / shares
6.5% Series F Preferred Shares [Member]
Dividends Payable [Line Items]
Series F	$ 64.55

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

No definition available.

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