Fair Value Of Financial Instruments (Schedule Of Changes In Fair Value Carrying Values Associated With Level 3 Financial Instruments) (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
	Sep. 30, 2015	Sep. 30, 2015
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Transfers, Out of Level 3	$ 0	$ (5,900)
Non-Agency [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Beginning Balance	670	806
Unrealized gains/(losses), Included in changes in net assets	(157)	(240)
Realized gains/(losses)	86	119
Redemptions	(199)	(285)
Net change	(270)	(406)
Ending Balance	400	400
Corporate Fixed Income Securities [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Beginning Balance	4,572	1,993
Unrealized gains/(losses), Included in changes in net assets	(126)	84
Realized gains/(losses)	53	53
Purchases		11,643
Sales	(4,499)	(13,773)
Net change	(4,572)	(1,993)
Equity Securities [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Beginning Balance	619	1,144
Sales		(525)
Net change		(525)
Ending Balance	619	619
Asset-Backed Securities [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Beginning Balance		44,045
Unrealized gains/(losses), Included in OCI, Assets		342
Realized gains/(losses)		(2,136)
Sales		(42,251)
Net change		(44,045)
Corporate Equity Securities [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Beginning Balance	2,962
Unrealized gains/(losses), Included in changes in net assets	269	354
Transfers, Into Level 3		2,877
Net change	269	3,231
Ending Balance	3,231	3,231
Equity Auction Rate Securities [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Beginning Balance	48,355	46,197
Unrealized gains/(losses), Included in changes in net assets	(631)	(873)
Purchases	8,500	15,125
Redemptions		(4,225)
Net change	7,869	10,027
Ending Balance	56,224	56,224
Municipal Auction Rate Securities [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Beginning Balance	1,324	1,326
Unrealized gains/(losses), Included in changes in net assets		(2)
Net change		(2)
Ending Balance	1,324	1,324
Other Investment [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Beginning Balance	69,242	72,990
Unrealized gains/(losses), Included in changes in net assets	(1,576)	2,392
Realized gains/(losses)	293	(210)
Purchases	1,117	4,396
Sales	(11,533)	(13,156)
Redemptions	(2,982)	(3,066)
Transfers, Out of Level 3		(8,785)
Net change	(14,681)	(18,429)
Ending Balance	$ 54,561	$ 54,561