Fair Value Measurement (Schedule Of Assets And Liabilities Measured At Fair Value On A Recurring Basis Valuation Techniques) (Details) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2012	Dec. 31, 2011
Fair Value Measurement [Line Items]
Assets	$ 3,113,130	$ 3,062,421
Liabilities	1,042	1,325
Level 1 [Member]
Fair Value Measurement [Line Items]
Assets	574,999	600,692
Liabilities	643	655
Level 2 [Member]
Fair Value Measurement [Line Items]
Assets	2,450,776	2,404,218
Liabilities	399	670
Level 3 [Member]
Fair Value Measurement [Line Items]
Assets	87,355	57,511
Liabilities	0	0
Short-term Investments [Member]
Fair Value Measurement [Line Items]
Assets	40,792	9,011
Short-term Investments [Member] | Level 1 [Member]
Fair Value Measurement [Line Items]
Assets	0	0
Short-term Investments [Member] | Level 2 [Member]
Fair Value Measurement [Line Items]
Assets	40,792	9,011
Short-term Investments [Member] | Level 3 [Member]
Fair Value Measurement [Line Items]
Assets	0	0
Money market instruments [Member]
Fair Value Measurement [Line Items]
Assets	138,534	227,433
Money market instruments [Member] | Level 1 [Member]
Fair Value Measurement [Line Items]
Assets	138,534	227,433
Money market instruments [Member] | Level 2 [Member]
Fair Value Measurement [Line Items]
Assets	0	0
Money market instruments [Member] | Level 3 [Member]
Fair Value Measurement [Line Items]
Assets	0	0
Equity contracts [Member]
Fair Value Measurement [Line Items]
Liabilities	643	655
Equity contracts [Member] | Level 1 [Member]
Fair Value Measurement [Line Items]
Liabilities	643	655
Equity contracts [Member] | Level 2 [Member]
Fair Value Measurement [Line Items]
Liabilities	0	0
Equity contracts [Member] | Level 3 [Member]
Fair Value Measurement [Line Items]
Liabilities	0	0
Interest rate swap agreements [Member]
Fair Value Measurement [Line Items]
Liabilities	399	670
Interest rate swap agreements [Member] | Level 1 [Member]
Fair Value Measurement [Line Items]
Liabilities	0	0
Interest rate swap agreements [Member] | Level 2 [Member]
Fair Value Measurement [Line Items]
Liabilities	399	670
Interest rate swap agreements [Member] | Level 3 [Member]
Fair Value Measurement [Line Items]
Liabilities	0	0
Fixed maturity securities [Member] | US government agencies debt securities [Member]
Fair Value Measurement [Line Items]
Assets	12,553	14,298
Fixed maturity securities [Member] | US government agencies debt securities [Member] | Level 1 [Member]
Fair Value Measurement [Line Items]
Assets	12,553	14,298
Fixed maturity securities [Member] | US government agencies debt securities [Member] | Level 2 [Member]
Fair Value Measurement [Line Items]
Assets	0	0
Fixed maturity securities [Member] | US government agencies debt securities [Member] | Level 3 [Member]
Fair Value Measurement [Line Items]
Assets	0	0
Fixed maturity securities [Member] | Municipal securities [Member]
Fair Value Measurement [Line Items]
Assets	2,265,322	2,271,275
Fixed maturity securities [Member] | Municipal securities [Member] | Level 1 [Member]
Fair Value Measurement [Line Items]
Assets	0	0
Fixed maturity securities [Member] | Municipal securities [Member] | Level 2 [Member]
Fair Value Measurement [Line Items]
Assets	2,265,322	2,271,275
Fixed maturity securities [Member] | Municipal securities [Member] | Level 3 [Member]
Fair Value Measurement [Line Items]
Assets	0	0
Fixed maturity securities [Member] | Mortgage-backed securities [Member]
Fair Value Measurement [Line Items]
Assets	30,887	37,371
Fixed maturity securities [Member] | Mortgage-backed securities [Member] | Level 1 [Member]
Fair Value Measurement [Line Items]
Assets	0	0
Fixed maturity securities [Member] | Mortgage-backed securities [Member] | Level 2 [Member]
Fair Value Measurement [Line Items]
Assets	30,887	37,371
Fixed maturity securities [Member] | Mortgage-backed securities [Member] | Level 3 [Member]
Fair Value Measurement [Line Items]
Assets	0	0
Fixed maturity securities [Member] | Corporate securities [Member]
Fair Value Measurement [Line Items]
Assets	102,550	75,142
Fixed maturity securities [Member] | Corporate securities [Member] | Level 1 [Member]
Fair Value Measurement [Line Items]
Assets	0	0
Fixed maturity securities [Member] | Corporate securities [Member] | Level 2 [Member]
Fair Value Measurement [Line Items]
Assets	102,550	75,142
Fixed maturity securities [Member] | Corporate securities [Member] | Level 3 [Member]
Fair Value Measurement [Line Items]
Assets	0	0
Fixed maturity securities [Member] | Collateralized debt obligations [Member]
Fair Value Measurement [Line Items]
Assets	76,325	47,503
Fixed maturity securities [Member] | Collateralized debt obligations [Member] | Level 1 [Member]
Fair Value Measurement [Line Items]
Assets	0	0
Fixed maturity securities [Member] | Collateralized debt obligations [Member] | Level 2 [Member]
Fair Value Measurement [Line Items]
Assets	0	0
Fixed maturity securities [Member] | Collateralized debt obligations [Member] | Level 3 [Member]
Fair Value Measurement [Line Items]
Assets	76,325	47,503
Equity securities [Member] | Public Utility, Equities [Member]
Fair Value Measurement [Line Items]
Assets	68,991	26,342
Equity securities [Member] | Public Utility, Equities [Member] | Level 1 [Member]
Fair Value Measurement [Line Items]
Assets	68,991	26,342
Equity securities [Member] | Public Utility, Equities [Member] | Level 2 [Member]
Fair Value Measurement [Line Items]
Assets	0	0
Equity securities [Member] | Public Utility, Equities [Member] | Level 3 [Member]
Fair Value Measurement [Line Items]
Assets	0	0
Equity securities [Member] | Banks, trusts and insurance, equities [Member]
Fair Value Measurement [Line Items]
Assets	18,483	16,027
Equity securities [Member] | Banks, trusts and insurance, equities [Member] | Level 1 [Member]
Fair Value Measurement [Line Items]
Assets	18,483	16,027
Equity securities [Member] | Banks, trusts and insurance, equities [Member] | Level 2 [Member]
Fair Value Measurement [Line Items]
Assets	0	0
Equity securities [Member] | Banks, trusts and insurance, equities [Member] | Level 3 [Member]
Fair Value Measurement [Line Items]
Assets	0	0
Equity securities [Member] | Energy and other [Member]
Fair Value Measurement [Line Items]
Assets	336,438	316,592
Equity securities [Member] | Energy and other [Member] | Level 1 [Member]
Fair Value Measurement [Line Items]
Assets	336,438	316,592
Equity securities [Member] | Energy and other [Member] | Level 2 [Member]
Fair Value Measurement [Line Items]
Assets	0	0
Equity securities [Member] | Energy and other [Member] | Level 3 [Member]
Fair Value Measurement [Line Items]
Assets	0	0
Equity securities [Member] | Non-redeemable preferred stock [Member]
Fair Value Measurement [Line Items]
Assets	11,225	11,419
Equity securities [Member] | Non-redeemable preferred stock [Member] | Level 1 [Member]
Fair Value Measurement [Line Items]
Assets	0	0
Equity securities [Member] | Non-redeemable preferred stock [Member] | Level 2 [Member]
Fair Value Measurement [Line Items]
Assets	11,225	11,419
Equity securities [Member] | Non-redeemable preferred stock [Member] | Level 3 [Member]
Fair Value Measurement [Line Items]
Assets	0	0
Equity securities [Member] | Partnership interest in a private credit fund [Member]
Fair Value Measurement [Line Items]
Assets	11,030	10,008
Equity securities [Member] | Partnership interest in a private credit fund [Member] | Level 1 [Member]
Fair Value Measurement [Line Items]
Assets	0	0
Equity securities [Member] | Partnership interest in a private credit fund [Member] | Level 2 [Member]
Fair Value Measurement [Line Items]
Assets	0	0
Equity securities [Member] | Partnership interest in a private credit fund [Member] | Level 3 [Member]
Fair Value Measurement [Line Items]
Assets	$ 11,030	$ 10,008