Fair Value Of Financial Instruments (Schedule Of Changes In Fair Value Associated With Level 3 Financial Instruments) (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
	Sep. 30, 2021	Sep. 30, 2021
Asset-Backed Securities [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Beginning Balance	$ 1,815	$ 9
Unrealized gains/(losses)		(3,000)
Realized gains		7,361
Purchases	68,028	68,104
Redemptions	(839)	(10,400)
Transfers out of Level 3	(70)	(70)
Category transfers		6,930
Net change	67,119	68,925
Ending Balance	68,934	68,934
Loans [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Beginning Balance	22,839	11,275
Unrealized gains/(losses)		(48)
Purchases	3,365	14,977
Sales	(7,350)	(7,350)
Net change	(3,985)	7,579
Ending Balance	18,854	18,854
Corporate Equity Securities [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Beginning Balance	8,754
Unrealized gains/(losses)	(1,000)	(1,000)
Purchases		3,000
Transfers into Level 3		5,754
Net change	(1,000)	7,754
Ending Balance	7,754	7,754
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)	(47)	(21)
Net change	(47)	(21)
Ending Balance	12,912	12,912
Other Investment [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Beginning Balance	34,666	42,113
Unrealized gains/(losses)	1,299	782
Category transfers		(6,930)
Net change	1,299	(6,148)
Ending Balance	$ 35,965	$ 35,965