Fair Value Measurement (Level 3 Assets and Liability) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2023	Mar. 31, 2022
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	$ 71,513	$ 57,565
Included in earnings, as a part of:
Included in earnings	13
Operating expense	0
Included in other comprehensive income (loss)	248	$ (1,253)
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
Purchases	8,185	$ 16,779
Sales	(432)	(1,140)
Transfers in	12,999	1,529
Transfers out	(8,015)	(5,023)
Ending balance	84,511	68,568
Change in unrealized gains (losses) included in earnings for the above period for Level 3 assets and liabilities held at period-end	$ (3)	$ 64
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:
Net investment gains (losses)	1,000	0
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	(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
Net Investment Income
Included in earnings, as a part of:
Included in earnings		$ 1
Fair Value, Asset, Recurring Basis, Unobservable Input Reconciliation, Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration]		Net investment income (loss)
Net investment gains (losses)
Included in earnings, as a part of:
Included in earnings		$ 110
Fair Value, Asset, Recurring Basis, Unobservable Input Reconciliation, Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration]		Gain (Loss) on Investments
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	63,973	$ 47,129
Included in earnings, as a part of:
Included in earnings	16	0
Operating expense	0
Included in other comprehensive income (loss)	209	(993)
Purchases	6,322	9,711
Sales	(432)	(1,019)
Transfers in	11,220	1,000
Transfers out	(5,151)	(2,503)
Ending balance	76,157	53,325
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	2,954	6,502
Included in earnings, as a part of:
Included in earnings	0	1
Operating expense	0
Included in other comprehensive income (loss)	39	(260)
Purchases	1,863	5,585
Sales	0	(5)
Transfers in	1,779	0
Transfers out	(1,581)	(2,520)
Ending balance	5,054	9,303
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	2,803	2,500
Included in earnings, as a part of:
Included in earnings	(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	2,800	2,500
Change in unrealized gains (losses) included in earnings for the above period for Level 3 assets and liabilities held at period-end	(3)	0
Other Investments
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	1,783	1,434
Included in earnings, as a part of:
Included in earnings	0	110
Operating expense	0
Included in other comprehensive income (loss)	0	0
Purchases	0	1,483
Sales	0	(116)
Transfers in	0	529
Transfers out	(1,283)	0
Ending balance	500	3,440
Change in unrealized gains (losses) included in earnings for the above period for Level 3 assets and liabilities held at period-end	0	64
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:
Net investment gains (losses)	1,000	0
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	(13,000)	(24,000)
Change in unrealized gains (losses) included in earnings for the above period for Level 3 assets and liabilities held at period-end	$ 0	$ 0