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, 2016	Sep. 30, 2016
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Transfers, Into Level 3		$ 500
Non-Agency [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Beginning Balance	$ 1,235	1,476
Unrealized gains/(losses), Included in changes in net assets		(18)
Realized gains/(losses)	42	51
Sales	(1)	(1)
Redemptions	(120)	(352)
Net change	(79)	(320)
Ending Balance	1,156	1,156
Fixed Income Securities [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Beginning Balance	292
Purchases		292
Redemptions	(13)	(13)
Net change	(13)	279
Ending Balance	279	279
Equity Securities [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Beginning Balance	619	619
Unrealized gains/(losses), Included in changes in net assets	(406)	(406)
Purchases	253	253
Net change	(153)	(153)
Ending Balance	466	466
Corporate Equity Securities [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Beginning Balance	4,529	2,942
Unrealized gains/(losses), Included in changes in net assets	816	2,403
Realized gains/(losses)	(999)	(999)
Sales	(1)	(1)
Net change	(184)	1,403
Ending Balance	4,345	4,345
Equity Auction Rate Securities [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Beginning Balance	50,750	50,442
Unrealized gains/(losses), Included in changes in net assets	57	840
Purchases	50	50
Redemptions	(250)	(725)
Net change	(143)	165
Ending Balance	50,607	50,607
Auction Rate Municipal Securities [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Beginning Balance	1,355	1,315
Unrealized gains/(losses), Included in changes in net assets	1	41
Net change	1	41
Ending Balance	1,356	1,356
Other Investment [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Beginning Balance	1,240	20
Purchases	3,027	3,782
Transfers, Into Level 3		465
Net change	3,027	4,247
Ending Balance	$ 4,267	$ 4,267