Derivatives and Hedging Activities (Schedule of Derivative Instruments, Gain (Loss) in Statement of Financial Performance) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013
Derivative Instruments, Gain (Loss) [Line Items]
Amount of gain (loss) recognized in income on derivative (ineffective portion, reclassifications of missed forecasted transactions and amounts excluded from effectiveness testing)	$ (8,048)	$ (5)
Interest Rate Swap [Member] | Cash Flow Hedging [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Amount of gain (loss) recognized in accumulated other comprehensive income on interest rate derivatives (effective portion)	2,636	(1,859)
Interest Rate Swap [Member] | Interest Expense [Member] | Cash Flow Hedging [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Amount of gain (loss) reclassified from accumulated other comprehensive income into income as interest expense (effective portion)	$ 0	$ 682