Fair Value Measurements and Derivative Instruments (Available-for-sale Securities Maturities) (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Amortized cost
Within 1 year	$ 14,398
After 1 year through 5 years	15,241
After 5 years through 10 years	66,618
After 10 years	264,606
Amortized cost	360,863	$ 325,421
Estimated fair value
Within 1 year	14,401
After 1 year through 5 years	15,266
After 5 years through 10 years	63,185
After 10 years	256,735
Total	$ 349,587	$ 325,794

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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