Fair Value Of Financial Instruments (Schedule Of Changes In Fair Value Carrying Values Associated With Level 3 Financial Instruments) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Transfers, Into Level 3	$ 1,300
Transfers, Out of Level 3	(6,300)
Non-Agency [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Beginning Balance	806
Unrealized gains/(losses), Included in changes in net assets	(241)	$ (127)
Realized gains/(losses)	127	13
Redemptions	(332)	(44)
Transfers, Into Level 3	1,116	964
Net change	670	806
Ending Balance	1,476	806
Corporate Fixed Income Securities [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Beginning Balance	1,993	2,039
Unrealized gains/(losses), Included in changes in net assets	84	(445)
Realized gains/(losses)	53	(1,320)
Purchases	11,643	8,549
Sales	(13,773)	(5,783)
Redemptions		(88)
Transfers, Out of Level 3		(959)
Net change	(1,993)	(46)
Ending Balance		1,993
Equity Securities [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Beginning Balance	1,144	241
Unrealized gains/(losses), Included in changes in net assets		(494)
Realized gains/(losses)		4,965
Purchases		1,394
Sales	(525)	(5,205)
Transfers, Into Level 3		243
Net change	(525)	903
Ending Balance	619	1,144
Asset-Backed Securities [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Beginning Balance	44,045	58,078
Unrealized gains/(losses), Included in OCI, Assets	342	(530)
Realized gains/(losses)	(2,136)	1,322
Sales	(42,251)	(4,825)
Redemptions		(10,000)
Net change	(44,045)	(14,033)
Ending Balance		44,045
Corporate Equity Securities [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Unrealized gains/(losses), Included in changes in net assets	1,410
Transfers, Into Level 3	7,732
Transfers, Out of Level 3	(4,841)
Net change	4,301
Ending Balance	4,301
Equity Auction Rate Securities [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Beginning Balance	46,197	56,693
Unrealized gains/(losses), Included in changes in net assets	(413)	604
Purchases	15,176	25
Sales		(1,725)
Redemptions	(5,250)	(9,400)
Transfers, Out of Level 3	(5,268)
Net change	4,245	(10,496)
Ending Balance	50,442	46,197
Municipal Auction Rate Securities [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Beginning Balance	1,326	10,939
Unrealized gains/(losses), Included in changes in net assets	(11)	688
Purchases		1,650
Sales		(10,324)
Redemptions		(1,627)
Net change	(11)	(9,613)
Ending Balance	1,315	1,326
Other Investment [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Beginning Balance	72,990	97,768
Unrealized gains/(losses), Included in changes in net assets	1,241	(18)
Unrealized gains/(losses), Included in OCI, Assets	(1,381)
Realized gains/(losses)		3,412
Purchases	26,659	3,630
Sales	(16,245)	(25,030)
Redemptions	(4,770)	(4,413)
Transfers, Into Level 3		1,524
Transfers, Out of Level 3	(8,618)	(3,883)
Net change	(3,114)	(24,778)
Ending Balance	$ 69,876	72,990
U S States And Political Subdivisions
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Beginning Balance		6,200
Unrealized gains/(losses), Included in OCI, Assets		62
Transfers, Out of Level 3		(6,262)
Net change		$ (6,200)