Fair Value Of Financial Instruments (Schedule Of Changes In Fair Value Carrying Values Associated With Level 3 Financial Instruments) (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2016 USD ($)
Non-Agency [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Beginning Balance	$ 1,476
Realized gains/(losses)	7
Redemptions	(50)
Net change	(43)
Ending Balance	1,433
Equity Securities [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Beginning Balance	619
Ending Balance	619
Corporate Equity Securities [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Beginning Balance	2,942
Unrealized gains/(losses), Included in changes in net assets	37
Net change	37
Ending Balance	2,979
Equity Auction Rate Securities [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Beginning Balance	50,442
Unrealized gains/(losses), Included in changes in net assets	422
Net change	422
Ending Balance	50,864
Municipal Auction Rate Securities [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Beginning Balance	1,315
Unrealized gains/(losses), Included in changes in net assets	36
Net change	36
Ending Balance	1,351
Other Investment [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Beginning Balance	20
Purchases	755
Net change	755
Ending Balance	$ 775