Investments - Amortized Cost and Fair Value of Available-for-sale Fixed Income Securities (Details) - USD ($) $ in Thousands	Sep. 30, 2022	Dec. 31, 2021
Amortized Cost
Due in one year or less	$ 206,921
Due after one year through five years	867,511
Due after five years through 10 years	515,276
Due after 10 years	526,093
ABS/CMBS/MBS	637,830
Total available-for-sale	2,753,631	$ 2,346,267
Fair Value
Due in one year or less	206,327
Due after one year through five years	818,569
Due after five years through 10 years	457,011
Due after 10 years	411,591
ABS/CMBS/MBS	558,541
Total available-for-sale	$ 2,452,039	$ 2,409,887