Summary Of Investments Other Than Investments In Related Parties (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Cost	$ 3,303,156	$ 3,264,525
Fair value	3,380,642	3,403,822
Amounts in the balance sheet	3,380,642	3,403,822
Fixed Maturity Securities [Member]
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Cost	2,804,275	2,503,494
Fair value	2,880,003	2,618,400
Amounts in the balance sheet	2,880,003	2,618,400
Fixed Maturity Securities [Member] | U.S. Government Bonds And Agencies [Member]
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Cost	22,542	16,028
Fair value	22,507	16,108
Amounts in the balance sheet	22,507	16,108
Fixed Maturity Securities [Member] | Municipal Securities [Member]
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Cost	2,417,046	2,160,710
Fair value	2,505,039	2,275,455
Amounts in the balance sheet	2,505,039	2,275,455
Fixed Maturity Securities [Member] | Collateralized Mortgage Backed Securities [Member]
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Cost	49,639	45,519
Fair value	49,839	47,691
Amounts in the balance sheet	49,839	47,691
Fixed Maturity Securities [Member] | Corporate Debt Securities [Member]
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Cost	255,606	258,940
Fair value	243,372	256,930
Amounts in the balance sheet	243,372	256,930
Fixed Maturity Securities [Member] | Collateralized Debt Obligations [Member]
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Cost	50,710	22,297
Fair value	50,548	22,216
Amounts in the balance sheet	50,548	22,216
Fixed Maturity Securities [Member] | Collateralized Auto Loans [Member]
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Cost	8,732
Fair value	8,698
Amounts in the balance sheet	8,698
Equity Securities [Member]
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Cost	313,528	387,851
Fair value	315,362	412,880
Amounts in the balance sheet	315,362	412,880
Equity Securities [Member] | Common Stock [Member]
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Cost	275,479	349,839
Fair value	280,263	372,598
Amounts in the balance sheet	280,263	372,598
Equity Securities [Member] | Non-Redeemable Preferred Stock [Member]
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Cost	25,161	28,012
Fair value	24,668	28,563
Amounts in the balance sheet	24,668	28,563
Equity Securities [Member] | Partnership Interest in a Private Credit Fund [Member]
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Cost	12,888	10,000
Fair value	10,431	11,719
Amounts in the balance sheet	10,431	11,719
Short-term Investments [Member]
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Cost	185,353	373,180
Fair value	185,277	372,542
Amounts in the balance sheet	$ 185,277	$ 372,542