Derivative Instruments (Fair Value of Cash Flow Derivative Instruments) (Details) - Designated as Hedging Instrument [Member] - Cash Flow Hedging [Member] - Interest rate contracts [Member] - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Other Noncurrent Assets [Member]
Derivatives Fair Value [Line Items]
Asset Derivatives, Fair Value	$ 1,601	$ 1,510
Other Long-term Obligations [Member]
Derivatives Fair Value [Line Items]
Liability Derivatives, Fair Value	$ 22,398	$ 2,888