Derivatives and Hedging Activities (Schedule of Derivative Instruments in Statement of Financial Position, Fair Value) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended	12 Months Ended
	Jun. 30, 2013	Dec. 31, 2012
Derivatives, Fair Value [Line Items]
Gross Amounts of Recognized Assets	$ 10,161	$ 0
Gross Amounts of Recognized Liabilities	(1,186)	(3,830)
Derivative Asset, Fair Value, Amount Offset Against Collateral	0	0
Net Amounts of Liabilities Presented in the Consolidated Balance Sheet	(1,186)	(3,830)
Financial Instruments	0	0
Cash Collateral Received	0	0
Derivative, Fair Value, Net	8,975	(3,830)
Interest Rate Swap [Member] | Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member]
Derivatives, Fair Value [Line Items]
Gross Amounts of Recognized Assets	(10,161)
Gross Amounts of Recognized Liabilities	$ (1,186)	$ 3,830