Fair Value Of Financial Instruments (Schedule Of Changes In Fair Value Associated With Level 3 Financial Instruments) (Details) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
	Jun. 30, 2021	Jun. 30, 2021
Asset-Backed Securities [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Beginning Balance	$ 9	$ 9
Unrealized gains/(losses)	(3,000)	(3,000)
Realized gains	7,361	7,361
Purchases	76	76
Redemptions	(9,561)	(9,561)
Category transfers	6,930	6,930
Net change	1,806	1,806
Ending Balance	1,815	1,815
Loans [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Beginning Balance	14,268	11,275
Unrealized gains/(losses)	(27)	(48)
Purchases	8,598	11,612
Net change	8,571	11,564
Ending Balance	22,839	22,839
Corporate Equity Securities [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Beginning Balance	2,000
Purchases	1,000	3,000
Transfers into Level 3	5,754	5,754
Net change	6,754	8,754
Ending Balance	8,754	8,754
Auction Rate Securities [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Beginning Balance	12,959	12,933
Unrealized gains/(losses)		26
Net change		26
Ending Balance	12,959	12,959
Other Investment [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Beginning Balance	41,828	42,113
Unrealized gains/(losses)	(232)	(517)
Category transfers	(6,930)	(6,930)
Net change	(7,162)	(7,447)
Ending Balance	$ 34,666	$ 34,666