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	Dec. 31, 2012	Dec. 31, 2011
Fair Value Measurement [Line Items]
Assets	$ 3,180,095	$ 3,062,421
Liabilities	278	1,325
Level 1 [Member]
Fair Value Measurement [Line Items]
Assets	738,408	600,692
Liabilities	175	655
Level 2 [Member]
Fair Value Measurement [Line Items]
Assets	2,387,580	2,404,218
Liabilities	103	670
Level 3 [Member]
Fair Value Measurement [Line Items]
Assets	54,107	57,511
Liabilities	0	0
Short-term bonds [Member]
Fair Value Measurement [Line Items]
Assets	24,530	9,011
Short-term bonds [Member] \| Level 1 [Member]
Fair Value Measurement [Line Items]
Assets	0	0
Short-term bonds [Member] \| Level 2 [Member]
Fair Value Measurement [Line Items]
Assets	24,530	9,011
Short-term bonds [Member] \| Level 3 [Member]
Fair Value Measurement [Line Items]
Assets	0	0
Money market instruments [Member]
Fair Value Measurement [Line Items]
Assets	270,123	227,433
Money market instruments [Member] \| Level 1 [Member]
Fair Value Measurement [Line Items]
Assets	270,123	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	175	655
Equity contracts [Member] \| Level 1 [Member]
Fair Value Measurement [Line Items]
Liabilities	175	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	103	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	103	670
Interest rate swap agreements [Member] \| Level 3 [Member]
Fair Value Measurement [Line Items]
Liabilities	0	0
Fixed Maturity Securities [Member] \| U.S. government bonds and agencies [Member]
Fair Value Measurement [Line Items]
Assets	14,204	14,298
Fixed Maturity Securities [Member] \| U.S. government bonds and agencies [Member] \| Level 1 [Member]
Fair Value Measurement [Line Items]
Assets	14,204	14,298
Fixed Maturity Securities [Member] \| U.S. government bonds and agencies [Member] \| Level 2 [Member]
Fair Value Measurement [Line Items]
Assets	0	0
Fixed Maturity Securities [Member] \| U.S. government bonds and agencies [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	2,165,095	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	2,165,095	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	30,703	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	30,703	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	155,551	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	155,551	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	42,801	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	42,801	47,503
Equity Securities [Member] \| Public utilities [Member]
Fair Value Measurement [Line Items]
Assets	85,106	26,342
Equity Securities [Member] \| Public utilities [Member] \| Level 1 [Member]
Fair Value Measurement [Line Items]
Assets	85,106	26,342
Equity Securities [Member] \| Public utilities [Member] \| Level 2 [Member]
Fair Value Measurement [Line Items]
Assets	0	0
Equity Securities [Member] \| Public utilities [Member] \| Level 3 [Member]
Fair Value Measurement [Line Items]
Assets	0	0
Equity Securities [Member] \| Banks, trusts and insurance companies [Member]
Fair Value Measurement [Line Items]
Assets	22,166	16,027
Equity Securities [Member] \| Banks, trusts and insurance companies [Member] \| Level 1 [Member]
Fair Value Measurement [Line Items]
Assets	22,166	16,027
Equity Securities [Member] \| Banks, trusts and insurance companies [Member] \| Level 2 [Member]
Fair Value Measurement [Line Items]
Assets	0	0
Equity Securities [Member] \| Banks, trusts and insurance companies [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	346,809	316,592
Equity Securities [Member] \| Energy and other [Member] \| Level 1 [Member]
Fair Value Measurement [Line Items]
Assets	346,809	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	11,701	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	11,701	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	11,306	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	$ 11,306	$ 10,008