Derivative Instruments - Not designated as hedging, Financial Performance (Details) (Not Designated as Hedging Instrument [Member], Interest Rate Swap [Member], Interest Expense [Member], USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Not Designated as Hedging Instrument [Member] | Interest Rate Swap [Member] | Interest Expense [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative Instruments, Loss Recognized in Income	$ 0	$ (1,480)	$ (80)