Derivative Instruments (Fair Value of Interest Rate Contracts Designated As Hedging Instruments) (Details) - Designated as Hedging Instrument [Member] - USD ($) $ in Thousands	Mar. 31, 2017	Dec. 31, 2016
Derivatives, Fair Value [Line Items]
Asset Derivatives, Fair Value	$ 1,385	$ 1,395
Liability Derivatives, Fair Value	219	91
Interest rate contracts [Member] | Other Current Assets [Member]
Derivatives, Fair Value [Line Items]
Asset Derivatives, Fair Value	158	32
Interest rate contracts [Member] | Other Noncurrent Assets [Member]
Derivatives, Fair Value [Line Items]
Asset Derivatives, Fair Value	1,227	1,363
Interest rate contracts [Member] | Other Long-term Obligations [Member]
Derivatives, Fair Value [Line Items]
Liability Derivatives, Fair Value	$ 219	$ 91