Investments - Amortized Cost and Estimated Fair Value, Net of Credit Loss Allowance, of Available-For-Sale Securities by Contractual Maturity (Details) $ in Thousands	Sep. 30, 2023 USD ($)
Amortized cost
Due in one year or less	$ 63,056
Due after one year through five years	431,382
Due after five years through ten years	171,654
Due after ten years	312,016
Amortized cost	978,108
Estimated fair value
Due in one year or less	61,957
Due after one year through five years	409,557
Due after five years through ten years	164,848
Due after ten years	278,875
Estimated fair value	$ 915,237