Derivatives and Hedging Activities (Schedule of Derivative Instruments in Statement of Financial Position, Fair Value) (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2014	Dec. 31, 2013
Derivatives, Fair Value [Line Items]
Derivative assets, at fair value	$ 9,829	$ 9,189
Derivative liabilities, at fair value	(35,471)	(18,455)
Series D Preferred Stock Embedded Derivative [Member] | Not Designated as Hedging Instrument [Member] | Derivative Liabilities, at Fair Value [Member]
Derivatives, Fair Value [Line Items]
Derivative liabilities, at fair value	(26,734)	(16,736)
Interest Rate Contract [Member] | Designated as Hedging Instrument [Member] | Derivative Liabilities, at Fair Value [Member]
Derivatives, Fair Value [Line Items]
Derivative liabilities, at fair value	(5,946)	(1,719)
Interest Rate Contract [Member] | Designated as Hedging Instrument [Member] | Deferred Costs and Other Assets, Net [Member]
Derivatives, Fair Value [Line Items]
Derivative assets, at fair value	8,301	9,189
Interest Rate Contract [Member] | Not Designated as Hedging Instrument [Member] | Derivative Liabilities, at Fair Value [Member]
Derivatives, Fair Value [Line Items]
Derivative liabilities, at fair value	(2,791)	0
Interest Rate Contract [Member] | Not Designated as Hedging Instrument [Member] | Deferred Costs and Other Assets, Net [Member]
Derivatives, Fair Value [Line Items]
Derivative assets, at fair value	$ 1,528	$ 0