Derivatives and Hedging Activities (Schedule of Derivative Instruments, Gain (Loss) in Statement of Financial Performance) (Details) (Interest Rate Swap [Member], Cash Flow Hedging [Member], USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011
Derivative Instruments, Gain (Loss) [Line Items]
Amount of gain (loss) recognized in accumulated other comprehensive income on interest rate derivatives (effective portion)	$ (4,684)	$ (111)
Derivative Instruments, Gain (Loss) Recognized in Income, Ineffective Portion and Amount Excluded from Effectiveness Testing, Net	(1)	0
Interest Expense [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative Instruments, Gain (Loss) Reclassified from Accumulated OCI into Income, Effective Portion, Net	$ (941)	$ (13)