Fair Value Of Financial Instruments (Schedule Of Changes In Fair Value Associated With Level 3 Financial Instruments) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021
Asset-Backed Securities [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Beginning Balance	$ 64,706	$ 9
Unrealized gains	$ 4,789	$ (3,002)
Fair Value, Asset, Recurring Basis, Unobservable Input Reconciliation, Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration]	OCI, Debt Securities, Available-for-Sale, Gain (Loss), after Adjustment and Tax	OCI, Debt Securities, Available-for-Sale, Gain (Loss), after Adjustment and Tax
Realized gains	$ 4,287	$ 9,485
Purchases	4,820	68,104
Redemptions	(76,423)	(16,750)
Transfers into Level 3		6,930
Transfers out of Level 3		(70)
Net change	(62,527)	64,697
Ending Balance	2,179	64,706
Corporate Equity Securities Financial Instruments Owned [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Beginning Balance	225
Realized gains	1,621
Sales	(1,846)
Transfers into Level 3		225
Net change	(225)	225
Ending Balance		225
Syndicated Loans [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Beginning Balance	26,857	11,275
Unrealized gains	$ 550	$ (68)
Fair Value, Asset, Recurring Basis, Unobservable Input Reconciliation, Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration]	OCI, Debt Securities, Available-for-Sale, Gain (Loss), after Adjustment and Tax	OCI, Debt Securities, Available-for-Sale, Gain (Loss), after Adjustment and Tax
Realized gains	$ 2,653
Purchases	227,548	$ 23,600
Sales	(177,895)	(7,725)
Redemptions	(9,825)
Transfers out of Level 3		(225)
Net change	43,031	15,582
Ending Balance	69,888	26,857
Corporate Equity Securities [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Beginning Balance	5,754
Unrealized gains	$ 6,124	$ (1,000)
Fair Value, Asset, Recurring Basis, Unobservable Input Reconciliation, Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration]	OCI, Debt Securities, Available-for-Sale, Gain (Loss), after Adjustment and Tax	OCI, Debt Securities, Available-for-Sale, Gain (Loss), after Adjustment and Tax
Purchases		$ 3,000
Sales		(2,000)
Transfers into Level 3		5,754
Net change	$ 6,124	5,754
Ending Balance	11,878	5,754
Auction Rate Securities [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Beginning Balance	13,032	12,933
Unrealized gains	$ 1,649	$ 124
Fair Value, Asset, Recurring Basis, Unobservable Input Reconciliation, Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration]	OCI, Debt Securities, Available-for-Sale, Gain (Loss), after Adjustment and Tax	OCI, Debt Securities, Available-for-Sale, Gain (Loss), after Adjustment and Tax
Redemptions		$ (25)
Net change	$ 1,649	99
Ending Balance	14,681	13,032
Other Investment [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Beginning Balance	35,837	42,113
Unrealized gains	$ 1,183	$ 654
Fair Value, Asset, Recurring Basis, Unobservable Input Reconciliation, Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration]	OCI, Debt Securities, Available-for-Sale, Gain (Loss), after Adjustment and Tax	OCI, Debt Securities, Available-for-Sale, Gain (Loss), after Adjustment and Tax
Realized gains	$ 992
Sales	(999)
Redemptions	(39)
Transfers out of Level 3		$ (6,930)
Net change	1,137	(6,276)
Ending Balance	$ 36,974	$ 35,837