Fair Value Measurements and Derivative Instruments (Long-term debt) (Details) - Designated as Hedging Instrument - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Carrying Amount of the Hedged Liabilities	$ 700,331	$ 715,234
Cumulative amount of Fair Value Hedging Adjustment Included in the Carrying Amount of the Hedged Liabilities	$ 17,512	$ (1,301)