Interest Rate Derivatives and Hedging Activities (Schedule of Derivative Instruments, Gain (Loss) in Statement of Financial Performance) (Details) (Cash Flow Hedging, Interest rate swaps, net, USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Derivative Instruments, Gain (Loss) [Line Items]
Amount of income (loss) recognized in accumulated other comprehensive loss from interest rate derivatives (effective portion)	$ (1,575)	$ 1,734	$ (2,232)	$ 1,699
Amount of income recognized in gain on derivative instruments (ineffective portion and amount excluded from effectiveness testing)	0	4	0	4
Interest Expense
Derivative Instruments, Gain (Loss) [Line Items]
Amount of loss reclassified from accumulated other comprehensive loss into income as interest expense (effective portion)	$ (540)	$ (220)	$ (1,071)	$ (434)