Reinsurance (Schedule Of Ceded Credit Risk by Reinsurer) (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012
Ceded Credit Risk [Line Items]
Ceded reserve at end of year	$ 1,533,103	$ 1,450,348
Credit Risk Reinsurers, Subtotal, Excluding Residual Market Pools [Member]
Ceded Credit Risk [Line Items]
Ceded reserve at end of year	1,064,602
Munich Re
Ceded Credit Risk [Line Items]
Ceded reserve at end of year	193,405
Lloyds of London
Ceded Credit Risk [Line Items]
Ceded reserve at end of year	117,059
Swiss Re
Ceded Credit Risk [Line Items]
Ceded reserve at end of year	104,096
Alleghany Group
Ceded Credit Risk [Line Items]
Ceded reserve at end of year	96,348
Partner Re
Ceded Credit Risk [Line Items]
Ceded reserve at end of year	67,116
Axis Capital
Ceded Credit Risk [Line Items]
Ceded reserve at end of year	65,580
Berkshire Hathaway
Ceded Credit Risk [Line Items]
Ceded reserve at end of year	53,118
Ace Group
Ceded Credit Risk [Line Items]
Ceded reserve at end of year	46,413
Hannover Re Group
Ceded Credit Risk [Line Items]
Ceded reserve at end of year	35,607
Everest Re
Ceded Credit Risk [Line Items]
Ceded reserve at end of year	29,253
Arch Capital Group
Ceded Credit Risk [Line Items]
Ceded reserve at end of year	25,782
Other Reinsurers
Ceded Credit Risk [Line Items]
Ceded reserve at end of year	230,825
Residual Market Pools
Ceded Credit Risk [Line Items]
Ceded reserve at end of year	$ 468,501