Derivatives and Hedging Activities (Schedule of Derivative Instruments in Statement of Financial Position, Fair Value) (Details) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2014	Dec. 31, 2013
Derivatives, Fair Value [Line Items]
Derivative asset	$ 5,522	$ 9,189
Series D Preferred Stock Embedded Derivative [Member] | Not Designated as Hedging Instrument [Member] | Deferred Rent, Derivative Liabilities and Other Liabilities [Member]
Derivatives, Fair Value [Line Items]
Derivative liability	(11,520)	(16,736)
Interest Rate Contract [Member] | Not Designated as Hedging Instrument [Member] | Deferred Rent, Derivative Liabilities and Other Liabilities [Member]
Derivatives, Fair Value [Line Items]
Derivative liability	(3,621)	0
Interest Rate Contract [Member] | Not Designated as Hedging Instrument [Member] | Deferred Costs and Other Assets, Net [Member]
Derivatives, Fair Value [Line Items]
Derivative asset	857	0
Cash Flow Hedging [Member] | Interest Rate Contract [Member] | Designated as Hedging Instrument [Member] | Derivative Liabilities, at Fair Value [Member]
Derivatives, Fair Value [Line Items]
Derivative liability	(9,190)	(1,719)
Cash Flow Hedging [Member] | Interest Rate Contract [Member] | Designated as Hedging Instrument [Member] | Deferred Costs and Other Assets, Net [Member]
Derivatives, Fair Value [Line Items]
Derivative asset	$ 4,665	$ 9,189