Reinsurance (Schedule Of Ceded Credit Risk by Reinsurer) (Details) - USD ($)	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Ceded Credit Risk [Line Items]
Uncollectible reinsurance	$ (7,712,903)	$ (7,800,649)	$ (690,127)
Ceded reserve at end of year	2,923,026,000
Credit Risk Reinsurers, Subtotal, Excluding Residual Market Pools [Member]
Ceded Credit Risk [Line Items]
Ceded reserve at end of year	2,717,501,000
Munich Re
Ceded Credit Risk [Line Items]
Ceded reserve at end of year	313,150,000
Lloyds of London
Ceded Credit Risk [Line Items]
Ceded reserve at end of year	308,119,000
Swiss Re
Ceded Credit Risk [Line Items]
Ceded reserve at end of year	203,165,000
Alleghany Group
Ceded Credit Risk [Line Items]
Ceded reserve at end of year	204,699,000
Partner Re
Ceded Credit Risk [Line Items]
Ceded reserve at end of year	231,251,000
Hannover Re Group
Ceded Credit Risk [Line Items]
Ceded reserve at end of year	167,906,000
Berkshire Hathaway
Ceded Credit Risk [Line Items]
Ceded reserve at end of year	126,806,000
Everest Re
Ceded Credit Risk [Line Items]
Ceded reserve at end of year	162,432,000
Lifson Re
Ceded Credit Risk [Line Items]
Ceded reserve at end of year	64,242,000
Renaissance Re
Ceded Credit Risk [Line Items]
Ceded reserve at end of year	138,408,000
Axis Capital
Ceded Credit Risk [Line Items]
Ceded reserve at end of year	88,938,000
Liberty Mutual
Ceded Credit Risk [Line Items]
Ceded reserve at end of year	85,367,000
Korean Re
Ceded Credit Risk [Line Items]
Ceded reserve at end of year	55,643,000
Fairfax Financial
Ceded Credit Risk [Line Items]
Ceded reserve at end of year	43,975,000
Axa Insurance
Ceded Credit Risk [Line Items]
Ceded reserve at end of year	40,014,000
Other Reinsurers Less than $20,000
Ceded Credit Risk [Line Items]
Ceded reserve at end of year	350,287,000
Residual Market Pools
Ceded Credit Risk [Line Items]
Ceded reserve at end of year	213,238,000
Markel Corp Group
Ceded Credit Risk [Line Items]
Ceded reserve at end of year	26,737,000
Arch Capital Group
Ceded Credit Risk [Line Items]
Ceded reserve at end of year	58,156,000
Sompo Holdings Group
Ceded Credit Risk [Line Items]
Ceded reserve at end of year	24,220,000
Helvetia Holdings Group
Ceded Credit Risk [Line Items]
Ceded reserve at end of year	$ 23,986,000