Income Taxes - Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Deferred tax assets
Net unrealized loss on investments	$ 88,065	$ 121,497
State income taxes	46,170	54,946
Goodwill and intangibles	29,197	30,782
Unearned premiums	24,948	26,108
Capitalized research and development	12,450	4,740
Accrued expenses	10,829	11,913
Lease liability	9,386	10,371
Differences in fair value of financial instruments	2,840	5,998
Loss reserves	2,805	3,102
Other	28,196	30,673
Total deferred tax assets	254,886	300,130
Deferred tax liabilities
Contingency reserve	755,481	587,722
Depreciation	5,795	10,031
Other	19,820	23,823
Total deferred tax liabilities	781,096	621,576
Less: Valuation allowance	63,354	69,637
Net deferred tax asset (liability)	$ (589,564)	$ (391,083)