Fair Value Measurements and Derivative Instruments (Available-for-sale Securities Maturities) (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Amortized cost
Within 1 year	$ 19,299
After 1 year through 5 years	9,354
After 5 years through 10 years	54,448
After 10 years	314,953
Total	398,054	$ 218,512
Estimated fair value
Within 1 year	19,379
After 1 year through 5 years	9,553
After 5 years through 10 years	53,476
After 10 years	312,066
Total	$ 394,474	$ 222,120

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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