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	Mar. 31, 2014	Dec. 31, 2013
Fair Value Measurement [Line Items]
Assets	$ 3,318,203	$ 3,159,962
Liabilities	426	140
Level 1 [Member]
Fair Value Measurement [Line Items]
Assets	644,226	558,750
Liabilities	426	140
Level 2 [Member]
Fair Value Measurement [Line Items]
Assets	2,661,251	2,582,712
Liabilities	0	0
Level 3 [Member]
Fair Value Measurement [Line Items]
Assets	12,726	16,850
Liabilities	0	0
Short-term bonds [Member]
Fair Value Measurement [Line Items]
Assets	86,866	52,888
Short-term bonds [Member] | Level 1 [Member]
Fair Value Measurement [Line Items]
Assets	69,986	39,998
Short-term bonds [Member] | Level 2 [Member]
Fair Value Measurement [Line Items]
Assets	16,880	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	216,694	262,888
Money market instruments [Member] | Level 1 [Member]
Fair Value Measurement [Line Items]
Assets	216,694	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	1,499	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	1,499	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	426	140
Equity contracts [Member] | Level 1 [Member]
Fair Value Measurement [Line Items]
Liabilities	426	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	16,132	16,096
Fixed maturity securities [Member] | U.S. government bonds and agencies [Member] | Level 1 [Member]
Fair Value Measurement [Line Items]
Assets	16,132	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	2,292,975	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	2,292,975	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	39,649	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	39,649	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	284,476	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	284,476	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	88,471	85,287
Equity securities [Member] | Public utilities [Member] | Level 1 [Member]
Fair Value Measurement [Line Items]
Assets	88,471	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	7,412	2,927
Equity securities [Member] | Banks, trusts and insurance companies [Member] | Level 1 [Member]
Fair Value Measurement [Line Items]
Assets	7,412	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	245,531	151,554
Equity securities [Member] | Energy and other [Member] | Level 1 [Member]
Fair Value Measurement [Line Items]
Assets	245,531	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	25,772	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	25,772	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	12,726	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	$ 12,726	$ 12,548