Fair Value Measurement (Schedule Of Assets And Liabilities Measured At Fair Value On A Recurring Basis Valuation Techniques) (Details) (USD $) | Jun. 30, 2014 | Dec. 31, 2013 |
In Thousands, unless otherwise specified |
Fair Value Measurement [Line Items] | ' | ' |
Assets | $3,391,882 | $3,159,962 |
Liabilities | 635 | 140 |
Level 1 [Member] | ' | ' |
Fair Value Measurement [Line Items] | ' | ' |
Assets | 645,068 | 558,750 |
Liabilities | 635 | 140 |
Level 2 [Member] | ' | ' |
Fair Value Measurement [Line Items] | ' | ' |
Assets | 2,733,848 | 2,584,362 |
Liabilities | 0 | 0 |
Level 3 [Member] | ' | ' |
Fair Value Measurement [Line Items] | ' | ' |
Assets | 12,966 | 16,850 |
Liabilities | 0 | 0 |
Short-term bonds [Member] | ' | ' |
Fair Value Measurement [Line Items] | ' | ' |
Assets | 84,738 | 52,888 |
Short-term bonds [Member] | Level 1 [Member] | ' | ' |
Fair Value Measurement [Line Items] | ' | ' |
Assets | 69,990 | 39,998 |
Short-term bonds [Member] | Level 2 [Member] | ' | ' |
Fair Value Measurement [Line Items] | ' | ' |
Assets | 14,748 | 12,890 |
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 | 144,674 | 262,888 |
Money market instruments [Member] | Level 1 [Member] | ' | ' |
Fair Value Measurement [Line Items] | ' | ' |
Assets | 144,674 | 262,888 |
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 |
Total Return Swap [Member] | ' | ' |
Fair Value Measurement [Line Items] | ' | ' |
Assets | 2,300 | 1,650 |
Total Return Swap [Member] | Level 1 [Member] | ' | ' |
Fair Value Measurement [Line Items] | ' | ' |
Assets | 0 | 0 |
Total Return Swap [Member] | Level 2 [Member] | ' | ' |
Fair Value Measurement [Line Items] | ' | ' |
Assets | 2,300 | 1,650 |
Total Return Swap [Member] | Level 3 [Member] | ' | ' |
Fair Value Measurement [Line Items] | ' | ' |
Assets | 0 | 0 |
Equity contracts [Member] | ' | ' |
Fair Value Measurement [Line Items] | ' | ' |
Liabilities | 635 | 140 |
Equity contracts [Member] | Level 1 [Member] | ' | ' |
Fair Value Measurement [Line Items] | ' | ' |
Liabilities | 635 | 140 |
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 |
Fixed maturity securities [Member] | U.S. government bonds and agencies [Member] | ' | ' |
Fair Value Measurement [Line Items] | ' | ' |
Assets | 15,993 | 16,096 |
Fixed maturity securities [Member] | U.S. government bonds and agencies [Member] | Level 1 [Member] | ' | ' |
Fair Value Measurement [Line Items] | ' | ' |
Assets | 15,993 | 16,096 |
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 | 2,353,566 | 2,235,323 |
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 | 2,353,566 | 2,235,323 |
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 | 38,817 | 40,247 |
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 | 38,817 | 40,247 |
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 | 296,252 | 264,685 |
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 | 296,252 | 264,685 |
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 | ' | 4,302 |
Fixed maturity securities [Member] | Collateralized Debt Obligations [Member] | Level 1 [Member] | ' | ' |
Fair Value Measurement [Line Items] | ' | ' |
Assets | ' | 0 |
Fixed maturity securities [Member] | Collateralized Debt Obligations [Member] | Level 2 [Member] | ' | ' |
Fair Value Measurement [Line Items] | ' | ' |
Assets | ' | 0 |
Fixed maturity securities [Member] | Collateralized Debt Obligations [Member] | Level 3 [Member] | ' | ' |
Fair Value Measurement [Line Items] | ' | ' |
Assets | ' | 4,302 |
Equity securities [Member] | Public utilities [Member] | ' | ' |
Fair Value Measurement [Line Items] | ' | ' |
Assets | 101,347 | 85,287 |
Equity securities [Member] | Public utilities [Member] | Level 1 [Member] | ' | ' |
Fair Value Measurement [Line Items] | ' | ' |
Assets | 101,347 | 85,287 |
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 | 8,415 | 2,927 |
Equity securities [Member] | Banks, trusts and insurance companies [Member] | Level 1 [Member] | ' | ' |
Fair Value Measurement [Line Items] | ' | ' |
Assets | 8,415 | 2,927 |
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 | 304,649 | 151,554 |
Equity securities [Member] | Energy and other [Member] | Level 1 [Member] | ' | ' |
Fair Value Measurement [Line Items] | ' | ' |
Assets | 304,649 | 151,554 |
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 | 28,165 | 29,567 |
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 | 28,165 | 29,567 |
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 | 12,966 | 12,548 |
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 | $12,966 | $12,548 |