Derivative Instruments (Fair Value of Cash Flow and Fair Value Derivative Instruments) (Details) - Designated as Hedging Instrument [Member] - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Derivatives, Fair Value [Line Items]
Asset Derivatives, Fair Value	$ 1,395	$ 581
Liability Derivatives, Fair Value	91
Interest rate contracts [Member] | Other Current Assets [Member]
Derivatives, Fair Value [Line Items]
Asset Derivatives, Fair Value	32	7
Interest rate contracts [Member] | Other Noncurrent Assets [Member]
Derivatives, Fair Value [Line Items]
Asset Derivatives, Fair Value	1,363	$ 574
Interest rate contracts [Member] | Long-term Debt [Member]
Derivatives, Fair Value [Line Items]
Liability Derivatives, Fair Value	$ 91