Investments - Cost and Fair Value, Net of Credit Loss Allowance, of Available-For-Sale Securities (Details) - USD ($) $ in Thousands	Sep. 30, 2022	Dec. 31, 2021
Available-for-sale securities
Amortized cost	$ 954,297
Estimated fair value	874,687
Corporate debt securities
Available-for-sale securities
Amortized cost	591,682	$ 565,997
Gross unrealized gains	186	9,663
Gross unrealized losses	44,675	2,495
Estimated fair value	547,193	573,165
Collateralized debt obligations
Available-for-sale securities
Amortized cost	105,938	115,344
Gross unrealized gains	6	456
Gross unrealized losses	5,273	338
Estimated fair value	100,671	115,462
Commercial mortgage-backed securities
Available-for-sale securities
Amortized cost	71,032	88,636
Gross unrealized gains	0	1,465
Gross unrealized losses	7,815	777
Estimated fair value	63,217	89,324
Residential mortgage-backed securities
Available-for-sale securities
Amortized cost	147,276	140,217
Gross unrealized gains	1	1,007
Gross unrealized losses	18,731	1,302
Estimated fair value	128,546	139,922
Other debt securities
Available-for-sale securities
Amortized cost	25,103	23,859
Gross unrealized gains	0	197
Gross unrealized losses	2,248	136
Estimated fair value	22,855	23,920
U.S. Treasury
Available-for-sale securities
Amortized cost	13,266	4,226
Gross unrealized gains	0	73
Gross unrealized losses	1,061	7
Estimated fair value	12,205	4,292
Available-for-sale securities
Available-for-sale securities
Amortized cost	954,297	938,279
Gross unrealized gains	193	12,861
Gross unrealized losses	79,803	5,055
Estimated fair value	$ 874,687	$ 946,085

Amount, before tax, of unrealized gain in accumulated other comprehensive income (AOCI) on 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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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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