Fair Value Of Financial Instruments (Schedule Of Fair Value Measurement Using Significant Unobservable Inputs Level Three) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2014		Mar. 31, 2013
Other invested assets [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Opening balance	$ 764,081		$ 655,888
Realized and unrealized gains (losses) included in net income	22,626		32,253
Purchases	89,199		73,210
Sales	(35,919)		(51,211)
Transfers into Level 3 from Level 2	0		0
Transfers out of Level 3 to Level 2	0	[1]	0	[1]
Ending balance	839,987		710,140
Mortgage-Backed [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Opening balance	147,338		167,825
Realized and unrealized gains (losses) included in net income	1,368		(1,189)
Purchases	14,110		0
Sales	(17,956)		(21,645)
Transfers into Level 3 from Level 2	0		19,813
Transfers out of Level 3 to Level 2	(10,799)	[1]	(9,384)	[1]
Ending balance	134,061		155,420
Asset-Backed [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Opening balance	93,413		62,246
Realized and unrealized gains (losses) included in net income	(864)		(97)
Purchases	7,493		2,461
Sales	(3,176)		(16,622)
Transfers into Level 3 from Level 2	606		0
Transfers out of Level 3 to Level 2	(16,238)	[1]	(7,085)	[1]
Ending balance	81,234		40,903
Equity securities [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Opening balance	73,904		54,680
Realized and unrealized gains (losses) included in net income	(9,821)		3,107
Purchases	0		0
Sales	(29,297)		0
Transfers into Level 3 from Level 2	0		0
Transfers out of Level 3 to Level 2	0	[1]	0	[1]
Ending balance	$ 34,786		$ 57,787

[1] Transfers out of Level 3 are primarily attributable to the availability of market observable information.