Fair Value Measurements and Derivative Instruments (Long-term debt) (Details) - Designated as Hedging Instrument - USD ($) $ in Thousands |
Dec. 31, 2018 |
Dec. 31, 2017 |
---|---|---|
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ||
Carrying Amount of the Hedged Liabilities | $ 725,486 | $ 749,155 |
Cumulative amount of Fair Value Hedging Adjustment Included in the Carrying Amount of the Hedged Liabilities | $ (24,766) | $ (34,813) |