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, 2013	Dec. 31, 2012
Fair Value Measurement [Line Items]
Assets	$ 3,176,297	$ 3,180,095
Liabilities	331	278
Level 1 [Member]
Fair Value Measurement [Line Items]
Assets	636,641	738,408
Liabilities	331	175
Level 2 [Member]
Fair Value Measurement [Line Items]
Assets	2,488,674	2,387,580
Liabilities	0	103
Level 3 [Member]
Fair Value Measurement [Line Items]
Assets	50,982	54,107
Liabilities	0	0
Short-term bonds [Member]
Fair Value Measurement [Line Items]
Assets	34,800	24,530
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	34,800	24,530
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	130,720	270,123
Money market instruments [Member] | Level 1 [Member]
Fair Value Measurement [Line Items]
Assets	130,720	270,123
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	331	175
Equity contracts [Member] | Level 1 [Member]
Fair Value Measurement [Line Items]
Liabilities	331	175
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
Interest rate swap agreements [Member] | Level 1 [Member]
Fair Value Measurement [Line Items]
Liabilities		0
Interest rate swap agreements [Member] | Level 2 [Member]
Fair Value Measurement [Line Items]
Liabilities		103
Interest rate swap agreements [Member] | Level 3 [Member]
Fair Value Measurement [Line Items]
Liabilities		0
Fixed maturity securities [Member] | U.S. government bonds and agencies [Member]
Fair Value Measurement [Line Items]
Assets	15,965	14,204
Fixed maturity securities [Member] | U.S. government bonds and agencies [Member] | Level 1 [Member]
Fair Value Measurement [Line Items]
Assets	15,965	14,204
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	2,143,070	2,165,095
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	2,143,070	2,165,095
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	34,176	30,703
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	34,176	30,703
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	249,849	155,551
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	249,849	155,551
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	38,992	42,801
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	38,992	42,801
Equity securities [Member] | Public utilities [Member]
Fair Value Measurement [Line Items]
Assets	107,942	85,106
Equity securities [Member] | Public utilities [Member] | Level 1 [Member]
Fair Value Measurement [Line Items]
Assets	107,942	85,106
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	23,603	22,166
Equity securities [Member] | Banks, trusts and insurance companies [Member] | Level 1 [Member]
Fair Value Measurement [Line Items]
Assets	23,603	22,166
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	358,411	346,809
Equity securities [Member] | Energy and other [Member] | Level 1 [Member]
Fair Value Measurement [Line Items]
Assets	358,411	346,809
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	26,779	11,701
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	26,779	11,701
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 Private Credit Fund [Member]
Fair Value Measurement [Line Items]
Assets	11,990	11,306
Equity securities [Member] | Partnership Interest In Private Credit Fund [Member] | Level 1 [Member]
Fair Value Measurement [Line Items]
Assets	0	0
Equity securities [Member] | Partnership Interest In Private Credit Fund [Member] | Level 2 [Member]
Fair Value Measurement [Line Items]
Assets	0	0
Equity securities [Member] | Partnership Interest In Private Credit Fund [Member] | Level 3 [Member]
Fair Value Measurement [Line Items]
Assets	$ 11,990	$ 11,306