Risk Management and Use of Derivative Financial Instruments - Terms and Fair Values of Derivative Financial Instruments (Parenthetical) (Details)	Dec. 31, 2017
Indenture IA (Preferred Trust I) [Member] \| LIBOR [Member]
Derivatives Fair Value [Line Items]
Derivative, Basis Spread on Variable Rate	1.25%

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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