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	Sep. 30, 2014	Dec. 31, 2013
Fair Value Measurement [Line Items]
Assets	$ 3,407,703	$ 3,159,962
Liabilities	1,635	140
Level 1 [Member]
Fair Value Measurement [Line Items]
Assets	743,125	558,750
Liabilities	348	140
Level 2 [Member]
Fair Value Measurement [Line Items]
Assets	2,651,908	2,584,362
Liabilities	1,287	0
Level 3 [Member]
Fair Value Measurement [Line Items]
Assets	12,670	16,850
Liabilities	0	0
Short-term bonds [Member]
Fair Value Measurement [Line Items]
Assets	88,673	52,888
Short-term bonds [Member] | Level 1 [Member]
Fair Value Measurement [Line Items]
Assets	69,994	39,998
Short-term bonds [Member] | Level 2 [Member]
Fair Value Measurement [Line Items]
Assets	18,679	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	202,652	262,888
Money market instruments [Member] | Level 1 [Member]
Fair Value Measurement [Line Items]
Assets	202,652	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		1,650
Liabilities	1,287
Total Return Swap [Member] | Level 1 [Member]
Fair Value Measurement [Line Items]
Assets		0
Liabilities	0
Total Return Swap [Member] | Level 2 [Member]
Fair Value Measurement [Line Items]
Assets		1,650
Liabilities	1,287
Total Return Swap [Member] | Level 3 [Member]
Fair Value Measurement [Line Items]
Assets		0
Liabilities	0
Equity contracts [Member]
Fair Value Measurement [Line Items]
Liabilities	348	140
Equity contracts [Member] | Level 1 [Member]
Fair Value Measurement [Line Items]
Liabilities	348	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	16,116	16,096
Fixed maturity securities [Member] | U.S. government bonds and agencies [Member] | Level 1 [Member]
Fair Value Measurement [Line Items]
Assets	16,116	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	2,280,217	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	2,280,217	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	38,156	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	38,156	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	285,378	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	285,378	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	129,325	85,287
Equity securities [Member] | Public utilities [Member] | Level 1 [Member]
Fair Value Measurement [Line Items]
Assets	129,325	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	8,566	2,927
Equity securities [Member] | Banks, trusts and insurance companies [Member] | Level 1 [Member]
Fair Value Measurement [Line Items]
Assets	8,566	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	316,472	151,554
Equity securities [Member] | Energy and other [Member] | Level 1 [Member]
Fair Value Measurement [Line Items]
Assets	316,472	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	29,478	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	29,478	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	12,670	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	$ 12,670	$ 12,548