Investments - Amortized Cost and Estimated Fair Value of Available-For-Sale Securities by Contractual Maturity (Details) $ in Thousands	Mar. 31, 2020 USD ($)
Amortized cost
Due in one year or less	$ 27,108
Due after one year through five years	344,995
Due after five years through ten years	134,580
Due after ten years	272,635
Amortized cost	779,318
Estimated fair value
Due in one year or less	26,764
Due after one year through five years	333,389
Due after five years through ten years	125,505
Due after ten years	265,995
Estimated fair value	$ 751,653

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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