Fair Value Measurement (Level 3 Assets and Liability) (Details) - USD ($) $ in Thousands	3 Months Ended
Mar. 31, 2024	Mar. 31, 2023
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	$ 97,154	$ 71,513
Included in earnings, as a part of:
Included in earnings	$ 85	$ 13
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), Net of Tax, Portion Attributable to Parent	Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent
Operating expense		$ 0
Included in other comprehensive income (loss)	$ (199)	248
Purchases	3,401	8,185
Sales	(702)	(432)
Transfers in	0	12,999
Transfers out	(25,414)	(8,015)
Ending balance	74,325	84,511
Change in unrealized gains (losses) included in earnings for the above period for Level 3 assets and liabilities held at period-end	$ 85	$ (3)
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	$ (6,500)	$ (15,000)
Total gains (losses) realized and unrealized:
Net investment gains (losses)	0	1,000
Operating expense		1,000
Included in other comprehensive income (loss)	0	0
Purchases	0	0
Sales	0	0
Transfers in	0	0
Transfers out	0	0
Ending balance	(6,500)
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)
Included in earnings, as a part of:
Fair Value, Asset, Recurring Basis, Unobservable Input Reconciliation, Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration]		Net Investment Income
Net investment gains (losses)
Included in earnings, as a part of:
Fair Value, Liability, Recurring Basis, Unobservable Input Reconciliation, Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration]	Gain (Loss) on Investments
Corporate Debt
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	$ 82,377	$ 63,973
Included in earnings, as a part of:
Included in earnings	0	16
Operating expense		0
Included in other comprehensive income (loss)	(171)	209
Purchases	2,201	6,322
Sales	(702)	(432)
Transfers in	0	11,220
Transfers out	(17,497)	(5,151)
Ending balance	66,208	76,157
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
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	4,414	2,954
Included in earnings, as a part of:
Included in earnings	0	0
Operating expense		0
Included in other comprehensive income (loss)	(28)	39
Purchases	1,200	1,863
Sales	0	0
Transfers in	0	1,779
Transfers out	(3,445)	(1,581)
Ending balance	2,141	5,054
Change in unrealized gains (losses) included in earnings for the above period for Level 3 assets and liabilities held at period-end	0	0
Equity Investments
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	5,237	2,803
Included in earnings, as a part of:
Included in earnings	(3)	(3)
Operating expense		0
Included in other comprehensive income (loss)	0	0
Purchases	0	0
Sales	0	0
Transfers in	0	0
Transfers out	0	0
Ending balance	5,234	2,800
Change in unrealized gains (losses) included in earnings for the above period for Level 3 assets and liabilities held at period-end	(3)	(3)
Other Investments
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	5,126	1,783
Included in earnings, as a part of:
Included in earnings	88	0
Operating expense		0
Included in other comprehensive income (loss)	0	0
Purchases	0	0
Sales	0	0
Transfers in	0	0
Transfers out	(4,472)	(1,283)
Ending balance	742	500
Change in unrealized gains (losses) included in earnings for the above period for Level 3 assets and liabilities held at period-end	88	0
Other Liabilities
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	(6,500)	(15,000)
Total gains (losses) realized and unrealized:
Net investment gains (losses)	0	1,000
Operating expense		1,000
Included in other comprehensive income (loss)	0	0
Purchases	0	0
Sales	0	0
Transfers in	0	0
Transfers out	0	0
Ending balance	(6,500)	(13,000)
Change in unrealized gains (losses) included in earnings for the above period for Level 3 assets and liabilities held at period-end	$ 0	$ 0

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Amount of unrealized gain (loss) recognized in income from asset measured at fair value on recurring basis using unobservable input (level 3) and still held.

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Amount of transfers of financial instrument classified as a liability into level 3 of the fair value hierarchy.

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Amount of transfers of financial instrument classified as a liability out of level 3 of the fair value hierarchy.

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Amount of gain (loss) recognized in income from asset measured at fair value on recurring basis using unobservable input (level 3).

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Amount of purchases of financial instrument classified as an asset measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing.

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