Fair Value Measurements and Derivative Instruments (Reconciliation) (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Amortized cost
Within 1 year	$ 35,393
After 1 year through 5 years	49,647
After 5 years through 10 years	59,265
After 10 years	74,207
Amortized cost	218,512	$ 270,313
Estimated fair value
Within 1 year	35,495
After 1 year through 5 years	50,426
After 5 years through 10 years	60,345
After 10 years	75,854
Total	$ 222,120	$ 265,329