Fair Value Measurements and Derivative Instruments (Reconciliation) (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Amortized cost
Within 1 year	$ 49,531
After 1 year through 5 years	107,848
After 5 years through 10 years	35,531
After 10 years	77,403
Amortized cost	270,313	$ 365,776
Estimated fair value
Within 1 year	49,286
After 1 year through 5 years	106,586
After 5 years through 10 years	34,627
After 10 years	74,830
Total	$ 265,329	$ 367,833

Amortized cost of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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