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, 2020	Sep. 30, 2020
Asset-Backed Securities [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Beginning Balance	$ 175	$ 175
Unrealized gains/(losses)	(166)	(166)
Net change	(166)	(166)
Ending Balance	9	9
Corporate Equity Securities [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Beginning Balance	1,060	1,060
Ending Balance	1,060	1,060
Equity Auction Rate Securities [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Beginning Balance	12,621	14,243
Unrealized gains/(losses)	(6)	(1,628)
Net change	(6)	(1,628)
Ending Balance	12,615	12,615
Auction Rate Municipal Securities [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Beginning Balance	183	184
Unrealized gains/(losses)		(1)
Net change		(1)
Ending Balance	183	183
Other Investment [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Beginning Balance	35,001	853
Unrealized gains/(losses)		(478)
Sales		(20)
Net change		34,148
Ending Balance	35,001	35,001
Transfers into Level 3		34,646
Loans [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Beginning Balance	9,611	9,151
Unrealized gains/(losses)	690	(2,923)
Purchases	667	7,748
Sales	(4,467)	(7,472)
Redemptions	1,000	(1,003)
Redemptions	(1,000)	1,003
Net change	(4,110)	(3,650)
Ending Balance	$ 5,501	$ 5,501