Fair Value Measurement (Schedule Of Assets And Liabilities Measured At Fair Value On A Recurring Basis Valuation Techniques) (Details) (USD $) In Thousands	Jun. 30, 2011	Dec. 31, 2010
Total assets at fair value	$ 3,118,504	$ 3,159,497
Total liabilities at fair value	4,059	5,818
Equity Securities [Member] | Public Utilities [Member]
Total assets at fair value	29,873	27,214
Equity Securities [Member] | Public Utilities [Member] | Level 1 [Member]
Total assets at fair value	29,873	27,214
Equity Securities [Member] | Public Utilities [Member] | Level 2 [Member]
Total assets at fair value	0	0
Equity Securities [Member] | Public Utilities [Member] | Level 3 [Member]
Total assets at fair value	0	0
Equity Securities [Member] | Banks, Trusts and Insurance Companies [Member]
Total assets at fair value	17,821	20,521
Equity Securities [Member] | Banks, Trusts and Insurance Companies [Member] | Level 1 [Member]
Total assets at fair value	17,821	20,521
Equity Securities [Member] | Banks, Trusts and Insurance Companies [Member] | Level 2 [Member]
Total assets at fair value	0	0
Equity Securities [Member] | Banks, Trusts and Insurance Companies [Member] | Level 3 [Member]
Total assets at fair value	0	0
Equity Securities [Member] | Industrial and Other [Member]
Total assets at fair value	362,041	302,103
Equity Securities [Member] | Industrial and Other [Member] | Level 1 [Member]
Total assets at fair value	362,041	302,103
Equity Securities [Member] | Industrial and Other [Member] | Level 2 [Member]
Total assets at fair value	0	0
Equity Securities [Member] | Industrial and Other [Member] | Level 3 [Member]
Total assets at fair value	0	0
Equity Securities [Member] | Non-Redeemable Preferred Stock [Member]
Total assets at fair value	12,232	9,768
Equity Securities [Member] | Non-Redeemable Preferred Stock [Member] | Level 1 [Member]
Total assets at fair value	0	0
Equity Securities [Member] | Non-Redeemable Preferred Stock [Member] | Level 2 [Member]
Total assets at fair value	12,232	9,768
Equity Securities [Member] | Non-Redeemable Preferred Stock [Member] | Level 3 [Member]
Total assets at fair value	0	0
Fixed Maturity Securities [Member] | U.S. Government Bonds and Agencies [Member]
Total assets at fair value	13,887	8,805
Fixed Maturity Securities [Member] | U.S. Government Bonds and Agencies [Member] | Level 1 [Member]
Total assets at fair value	13,887	8,805
Fixed Maturity Securities [Member] | U.S. Government Bonds and Agencies [Member] | Level 2 [Member]
Total assets at fair value	0	0
Fixed Maturity Securities [Member] | U.S. Government Bonds and Agencies [Member] | Level 3 [Member]
Total assets at fair value	0	0
Fixed Maturity Securities [Member] | Municipal Securities [Member]
Total assets at fair value	2,355,028	2,435,213
Fixed Maturity Securities [Member] | Municipal Securities [Member] | Level 1 [Member]
Total assets at fair value	0	0
Fixed Maturity Securities [Member] | Municipal Securities [Member] | Level 2 [Member]
Total assets at fair value	2,355,028	2,433,589
Fixed Maturity Securities [Member] | Municipal Securities [Member] | Level 3 [Member]
Total assets at fair value	0	1,624
Fixed Maturity Securities [Member] | Mortgage-Backed Securities [Member]
Total assets at fair value	45,006	57,367
Fixed Maturity Securities [Member] | Mortgage-Backed Securities [Member] | Level 1 [Member]
Total assets at fair value	0	0
Fixed Maturity Securities [Member] | Mortgage-Backed Securities [Member] | Level 2 [Member]
Total assets at fair value	45,006	57,367
Fixed Maturity Securities [Member] | Mortgage-Backed Securities [Member] | Level 3 [Member]
Total assets at fair value	0	0
Fixed Maturity Securities [Member] | Corporate Securities [Member]
Total assets at fair value	87,319	95,203
Fixed Maturity Securities [Member] | Corporate Securities [Member] | Level 1 [Member]
Total assets at fair value	0	0
Fixed Maturity Securities [Member] | Corporate Securities [Member] | Level 2 [Member]
Total assets at fair value	87,319	95,203
Fixed Maturity Securities [Member] | Corporate Securities [Member] | Level 3 [Member]
Total assets at fair value	0	0
Fixed Maturity Securities [Member] | Collateralized Debt Obligations [Member]
Total assets at fair value	55,724	55,692
Fixed Maturity Securities [Member] | Collateralized Debt Obligations [Member] | Level 1 [Member]
Total assets at fair value	0	0
Fixed Maturity Securities [Member] | Collateralized Debt Obligations [Member] | Level 2 [Member]
Total assets at fair value	0	0
Fixed Maturity Securities [Member] | Collateralized Debt Obligations [Member] | Level 3 [Member]
Total assets at fair value	55,724	55,692
Short Term Bond [Member]
Total assets at fair value	11,966	17,043
Short Term Bond [Member] | Level 1 [Member]
Total assets at fair value	0	0
Short Term Bond [Member] | Level 2 [Member]
Total assets at fair value	11,966	17,043
Short Term Bond [Member] | Level 3 [Member]
Total assets at fair value	0	0
Money Market Instruments [Member]
Total assets at fair value	126,070	126,328
Money Market Instruments [Member] | Level 1 [Member]
Total assets at fair value	126,070	126,328
Money Market Instruments [Member] | Level 2 [Member]
Total assets at fair value	0	0
Money Market Instruments [Member] | Level 3 [Member]
Total assets at fair value	0	0
Interest Rate Swap Agreements [Member]
Total assets at fair value	902	4,240
Total liabilities at fair value	2,010	3,042
Interest Rate Swap Agreements [Member] | Level 1 [Member]
Total assets at fair value	0	0
Total liabilities at fair value	0	0
Interest Rate Swap Agreements [Member] | Level 2 [Member]
Total assets at fair value	902	4,240
Total liabilities at fair value	2,010	3,042
Interest Rate Swap Agreements [Member] | Level 3 [Member]
Total assets at fair value	0	0
Total liabilities at fair value	0	0
Equity Contracts [Member]
Total assets at fair value	635
Total liabilities at fair value	2,049	2,776
Equity Contracts [Member] | Level 1 [Member]
Total assets at fair value	635
Total liabilities at fair value	2,049	2,776
Equity Contracts [Member] | Level 2 [Member]
Total assets at fair value	0
Total liabilities at fair value	0	0
Equity Contracts [Member] | Level 3 [Member]
Total assets at fair value	0
Total liabilities at fair value	0	0
Level 1 [Member]
Total assets at fair value	550,327	484,971
Total liabilities at fair value	2,049	2,776
Level 2 [Member]
Total assets at fair value	2,512,453	2,617,210
Total liabilities at fair value	2,010	3,042
Level 3 [Member]
Total assets at fair value	55,724	57,316
Total liabilities at fair value	$ 0	$ 0