Fair Value Measurements (Details) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2012	Dec. 31, 2011
Fair value measurements for investments in available-for-sale fixed maturity and equity securities
Available-for-sale Securities, Fair Value Disclosure	$ 690,062	$ 654,036
Assets and liabilities on recurring basis [Member]
Fair value measurements for investments in available-for-sale fixed maturity and equity securities
Available-for-sale Securities, Fair Value Disclosure	690,062	654,036
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Assets and liabilities on recurring basis [Member]
Fair value measurements for investments in available-for-sale fixed maturity and equity securities
Available-for-sale Securities, Fair Value Disclosure	1,127	6,178
Significant Other Observable Inputs (Level 2) [Member] | Assets and liabilities on recurring basis [Member]
Fair value measurements for investments in available-for-sale fixed maturity and equity securities
Available-for-sale Securities, Fair Value Disclosure	688,935	647,858
Significant Unobservable Inputs (Level 3) [Member] | Assets and liabilities on recurring basis [Member]
Fair value measurements for investments in available-for-sale fixed maturity and equity securities
Available-for-sale Securities, Fair Value Disclosure
U.S. Treasury securities and obligations of U.S. government corporations and agencies [Member] | Assets and liabilities on recurring basis [Member]
Fair value measurements for investments in available-for-sale fixed maturity and equity securities
Available-for-sale Securities, Fair Value Disclosure	76,972	60,978
U.S. Treasury securities and obligations of U.S. government corporations and agencies [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Assets and liabilities on recurring basis [Member]
Fair value measurements for investments in available-for-sale fixed maturity and equity securities
Available-for-sale Securities, Fair Value Disclosure
U.S. Treasury securities and obligations of U.S. government corporations and agencies [Member] | Significant Other Observable Inputs (Level 2) [Member] | Assets and liabilities on recurring basis [Member]
Fair value measurements for investments in available-for-sale fixed maturity and equity securities
Available-for-sale Securities, Fair Value Disclosure	76,972	60,978
U.S. Treasury securities and obligations of U.S. government corporations and agencies [Member] | Significant Unobservable Inputs (Level 3) [Member] | Assets and liabilities on recurring basis [Member]
Fair value measurements for investments in available-for-sale fixed maturity and equity securities
Available-for-sale Securities, Fair Value Disclosure
Obligations of states and political subdivisions [Member] | Assets and liabilities on recurring basis [Member]
Fair value measurements for investments in available-for-sale fixed maturity and equity securities
Available-for-sale Securities, Fair Value Disclosure	412,572	398,877
Obligations of states and political subdivisions [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Assets and liabilities on recurring basis [Member]
Fair value measurements for investments in available-for-sale fixed maturity and equity securities
Available-for-sale Securities, Fair Value Disclosure
Obligations of states and political subdivisions [Member] | Significant Other Observable Inputs (Level 2) [Member] | Assets and liabilities on recurring basis [Member]
Fair value measurements for investments in available-for-sale fixed maturity and equity securities
Available-for-sale Securities, Fair Value Disclosure	412,572	398,877
Obligations of states and political subdivisions [Member] | Significant Unobservable Inputs (Level 3) [Member] | Assets and liabilities on recurring basis [Member]
Fair value measurements for investments in available-for-sale fixed maturity and equity securities
Available-for-sale Securities, Fair Value Disclosure
Corporate securities [Member] | Assets and liabilities on recurring basis [Member]
Fair value measurements for investments in available-for-sale fixed maturity and equity securities
Available-for-sale Securities, Fair Value Disclosure	74,253	64,114
Corporate securities [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Assets and liabilities on recurring basis [Member]
Fair value measurements for investments in available-for-sale fixed maturity and equity securities
Available-for-sale Securities, Fair Value Disclosure
Corporate securities [Member] | Significant Other Observable Inputs (Level 2) [Member] | Assets and liabilities on recurring basis [Member]
Fair value measurements for investments in available-for-sale fixed maturity and equity securities
Available-for-sale Securities, Fair Value Disclosure	74,253	64,114
Corporate securities [Member] | Significant Unobservable Inputs (Level 3) [Member] | Assets and liabilities on recurring basis [Member]
Fair value measurements for investments in available-for-sale fixed maturity and equity securities
Available-for-sale Securities, Fair Value Disclosure
Residential mortgage-backed securities [Member] | Assets and liabilities on recurring basis [Member]
Fair value measurements for investments in available-for-sale fixed maturity and equity securities
Available-for-sale Securities, Fair Value Disclosure	123,682	122,630
Residential mortgage-backed securities [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Assets and liabilities on recurring basis [Member]
Fair value measurements for investments in available-for-sale fixed maturity and equity securities
Available-for-sale Securities, Fair Value Disclosure
Residential mortgage-backed securities [Member] | Significant Other Observable Inputs (Level 2) [Member] | Assets and liabilities on recurring basis [Member]
Fair value measurements for investments in available-for-sale fixed maturity and equity securities
Available-for-sale Securities, Fair Value Disclosure	123,682	122,630
Residential mortgage-backed securities [Member] | Significant Unobservable Inputs (Level 3) [Member] | Assets and liabilities on recurring basis [Member]
Fair value measurements for investments in available-for-sale fixed maturity and equity securities
Available-for-sale Securities, Fair Value Disclosure
Equity securities [Member] | Assets and liabilities on recurring basis [Member]
Fair value measurements for investments in available-for-sale fixed maturity and equity securities
Available-for-sale Securities, Fair Value Disclosure	2,583	7,437
Equity securities [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Assets and liabilities on recurring basis [Member]
Fair value measurements for investments in available-for-sale fixed maturity and equity securities
Available-for-sale Securities, Fair Value Disclosure	1,127	6,178
Equity securities [Member] | Significant Other Observable Inputs (Level 2) [Member] | Assets and liabilities on recurring basis [Member]
Fair value measurements for investments in available-for-sale fixed maturity and equity securities
Available-for-sale Securities, Fair Value Disclosure	1,456	1,259
Equity securities [Member] | Significant Unobservable Inputs (Level 3) [Member] | Assets and liabilities on recurring basis [Member]
Fair value measurements for investments in available-for-sale fixed maturity and equity securities
Available-for-sale Securities, Fair Value Disclosure