Investments (Summary Of Changes In Net Unrealized Appreciation (Depreciation) For The Company's Investments) (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010
Schedule of Available-for-sale Securities [Line Items]
Change in unrealized appreciation (depreciation), pre-tax	$ 106,559	$ 48,437
Fixed maturity securities, other-than-temporary impairment	824	7,831
Deferred tax benefit (expense)	(26,484)	10,726
Deferred tax benefit (expense), other-than-temporary impairment	66	1,001
Change in unrealized appreciation (depreciation), net of deferred taxes, included in shareholders' equity	80,141	60,164
Equity Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Change in unrealized appreciation (depreciation), pre-tax	(15,143)	(1,878)
Other Invested Assets [Member]
Schedule of Available-for-sale Securities [Line Items]
Change in unrealized appreciation (depreciation), pre-tax	(1,515)	2,389
Fixed Maturity Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Change in unrealized appreciation (depreciation), pre-tax	$ 122,393	$ 40,095