Fair Value Measurement - Level 3 Assets & Liabilities (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation:
Beginning Balance	$ 71,513	$ 57,565
Total gains (losses) realized and unrealized:
Fair Value, Asset, Recurring Basis, Unobservable Input Reconciliation, Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration]	Operating expense
Operating expense	$ 0
Fair Value, Liability, Recurring Basis, Unobservable Input Reconciliation, Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration]	Gain (Loss) on Investments	Gain (Loss) on Investments
Included in other comprehensive income (loss)	$ (192)	$ (4,944)
Fair Value, Asset, Recurring Basis, Unobservable Input Reconciliation, Asset, Gain (Loss), Statement of Other Comprehensive Income or Comprehensive Income [Extensible Enumeration]	Other comprehensive income (loss), after tax, net of reclassification adjustments	Other comprehensive income (loss), after tax, net of reclassification adjustments
Purchases	$ 45,029	$ 49,771
Sales	(9,932)	(6,607)
Transfers in	20,762	22,304
Transfers out	(29,591)	(46,132)
Ending Balance	97,154	71,513
Change in unrealized gains (losses) included in earnings for the above period for Level 3 assets and liabilities held at period-end	$ (624)	$ (721)
Fair Value Asset Recurring Basis Still Held Unrealized Gain Loss Statement Of Income Extensible List Not Disclosed Flag	Change in unrealized gains (losses) included in earnings for the above period for Level 3 assets and liabilities held at period-end	Change in unrealized gains (losses) included in earnings for the above period for Level 3 assets and liabilities held at period-end
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	$ 15,000	$ 24,000
Total gains (losses) realized and unrealized:
Included in earnings	5,000	9,000
Operating expense	3,500
Purchases	0	0
Sales	0	0
Transfers in	0	0
Transfers out	0	0
Ending balance	6,500	15,000
Change in unrealized gains (losses) included in earnings for the above period for Level 3 assets and liabilities held at period-end	0	0
Net investment income (loss)
Total gains (losses) realized and unrealized:
Included in earnings	$ (23)	$ 7
Fair Value, Asset, Recurring Basis, Unobservable Input Reconciliation, Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration]	Net investment income	Net investment income
Net investment gains (losses)
Total gains (losses) realized and unrealized:
Included in earnings	$ (412)	$ (451)
Fair Value, Asset, Recurring Basis, Unobservable Input Reconciliation, Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration]	Gain (Loss) on Investments	Gain (Loss) on Investments
State and municipal bonds
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation:
Beginning Balance	$ 0
Total gains (losses) realized and unrealized:
Included in other comprehensive income (loss)	(19)
Purchases	750
Sales	0
Transfers in	0
Transfers out	(731)
Ending Balance	0	$ 0
Change in unrealized gains (losses) included in earnings for the above period for Level 3 assets and liabilities held at period-end	0
State and municipal bonds | Net investment income (loss)
Total gains (losses) realized and unrealized:
Included in earnings	0
State and municipal bonds | Net investment gains (losses)
Total gains (losses) realized and unrealized:
Included in earnings	0
Corporate debt
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation:
Beginning Balance	63,973	47,129
Total gains (losses) realized and unrealized:
Operating expense	0
Included in other comprehensive income (loss)	165	(4,324)
Purchases	34,311	34,805
Sales	(9,534)	(5,153)
Transfers in	14,666	18,828
Transfers out	(21,393)	(27,311)
Ending Balance	82,377	63,973
Change in unrealized gains (losses) included in earnings for the above period for Level 3 assets and liabilities held at period-end	0	0
Corporate debt | Net investment income (loss)
Total gains (losses) realized and unrealized:
Included in earnings	(23)	(1)
Corporate debt | Net investment gains (losses)
Total gains (losses) realized and unrealized:
Included in earnings	212	0
Asset-backed Securities
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation:
Beginning Balance	2,954	6,502
Total gains (losses) realized and unrealized:
Operating expense	0
Included in other comprehensive income (loss)	(357)	(601)
Purchases	3,253	10,907
Sales	(398)	(287)
Transfers in	3,988	570
Transfers out	(5,026)	(14,145)
Ending Balance	4,414	2,954
Change in unrealized gains (losses) included in earnings for the above period for Level 3 assets and liabilities held at period-end	0	0
Asset-backed Securities | Net investment income (loss)
Total gains (losses) realized and unrealized:
Included in earnings	0	8
Asset-backed Securities | Net investment gains (losses)
Total gains (losses) realized and unrealized:
Included in earnings	0	0
Equity Investments
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation:
Beginning Balance	2,803	2,500
Total gains (losses) realized and unrealized:
Included in earnings	(737)	102
Operating expense	0
Purchases	3,171	17
Sales	0	0
Transfers in	0	2,377
Transfers out	0	(2,193)
Ending Balance	5,237	2,803
Change in unrealized gains (losses) included in earnings for the above period for Level 3 assets and liabilities held at period-end	(737)	101
Other Investments
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation:
Beginning Balance	1,783	1,434
Total gains (losses) realized and unrealized:
Included in earnings	113	(553)
Operating expense	0
Purchases	4,294	3,292
Sales	0	(1,167)
Transfers in	2,108	529
Transfers out	(3,172)	(1,752)
Ending Balance	5,126	1,783
Change in unrealized gains (losses) included in earnings for the above period for Level 3 assets and liabilities held at period-end	113	(822)
Other Liabilities
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	15,000	24,000
Total gains (losses) realized and unrealized:
Included in earnings	5,000	9,000
Operating expense	3,500
Purchases	0	0
Sales	0	0
Transfers in	0	0
Transfers out	0	0
Ending balance	6,500	15,000
Change in unrealized gains (losses) included in earnings for the above period for Level 3 assets and liabilities held at period-end	$ 0	$ 0