Derivative Instruments - Designated as hedging, Financial Position (Details) - Interest Rate Swap [Member] - Cash Flow Hedging [Member] - Designated as Hedging Instrument [Member] - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Derivatives, Fair Value [Line Items]
Liability Derivatives	$ (4,070)	$ (2,900)
Prepaid Expenses and Other Current Assets [Member]
Derivatives, Fair Value [Line Items]
Asset Derivatives	160	0
Other Assets [Member]
Derivatives, Fair Value [Line Items]
Asset Derivatives	0	430
Accrued Liabilities [Member]
Derivatives, Fair Value [Line Items]
Liability Derivatives	(870)	(150)
Other long-term liabilities [Member]
Derivatives, Fair Value [Line Items]
Liability Derivatives	$ (3,360)	$ (3,180)