Investments (Details) (USD $)	Sep. 30, 2012	Dec. 31, 2011
Held to Maturity
Held to maturity, amortized cost	$ 43,888,265	$ 58,489,619
Held to Maturity, Gross Unrealized Gains	2,060,000	2,933,000
Held to Maturity, Gross Unrealized Losses		1,000
Total Held to Maturity, Estimated Fair Value	45,948,000	61,422,000
Available for Sale
Available for Sale, Amortized Cost	646,350,000	621,538,000
Available for Sale, Gross Unrealized Gains	44,075,000	33,516,000
Available for Sale, Gross Unrealized Losses	363,000	1,018,000
Available for Sale, Estimated Fair Value	690,062,000	654,036,000
U.S. Treasury securities and obligations of U.S. government corporations and agencies [Member]
Held to Maturity
Held to maturity, amortized cost	1,000,000	1,000,000
Held to Maturity, Gross Unrealized Gains	23,000	54,000
Held to Maturity, Gross Unrealized Losses
Total Held to Maturity, Estimated Fair Value	1,023,000	1,054,000
Available for Sale
Available for Sale, Amortized Cost	75,426,000	59,432,000
Available for Sale, Gross Unrealized Gains	1,557,000	1,546,000
Available for Sale, Gross Unrealized Losses	11,000
Available for Sale, Estimated Fair Value	76,972,000	60,978,000
Obligations of states and political subdivisions [Member]
Held to Maturity
Held to maturity, amortized cost	42,437,000	56,966,000
Held to Maturity, Gross Unrealized Gains	2,020,000	2,857,000
Held to Maturity, Gross Unrealized Losses
Total Held to Maturity, Estimated Fair Value	44,457,000	59,823,000
Available for Sale
Available for Sale, Amortized Cost	378,337,000	372,663,000
Available for Sale, Gross Unrealized Gains	34,297,000	26,252,000
Available for Sale, Gross Unrealized Losses	62,000	39,000
Available for Sale, Estimated Fair Value	412,572,000	398,876,000
Corporate securities [Member]
Held to Maturity
Held to maturity, amortized cost	250,000	250,000
Held to Maturity, Gross Unrealized Gains	1,000	3,000
Held to Maturity, Gross Unrealized Losses
Total Held to Maturity, Estimated Fair Value	251,000	253,000
Available for Sale
Available for Sale, Amortized Cost	70,680,000	62,837,000
Available for Sale, Gross Unrealized Gains	3,735,000	1,805,000
Available for Sale, Gross Unrealized Losses	162,000	528,000
Available for Sale, Estimated Fair Value	74,253,000	64,114,000
Residential mortgage-backed securities [Member]
Held to Maturity
Held to maturity, amortized cost	201,000	274,000
Held to Maturity, Gross Unrealized Gains	16,000	19,000
Held to Maturity, Gross Unrealized Losses		1,000
Total Held to Maturity, Estimated Fair Value	217,000	292,000
Available for Sale
Available for Sale, Amortized Cost	119,445,000	119,367,000
Available for Sale, Gross Unrealized Gains	4,342,000	3,307,000
Available for Sale, Gross Unrealized Losses	105,000	44,000
Available for Sale, Estimated Fair Value	123,682,000	122,630,000
Fixed maturities [Member]
Available for Sale
Available for Sale, Amortized Cost	643,888,000	614,299,000
Available for Sale, Gross Unrealized Gains	43,931,000	32,910,000
Available for Sale, Gross Unrealized Losses	340,000	611,000
Available for Sale, Estimated Fair Value	687,479,000	646,598,000
Equity securities [Member]
Available for Sale
Available for Sale, Amortized Cost	2,462,000	7,239,000
Available for Sale, Gross Unrealized Gains	144,000	606,000
Available for Sale, Gross Unrealized Losses	23,000	407,000
Available for Sale, Estimated Fair Value	$ 2,583,000	$ 7,438,000

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This item represents the cost of debt and equity securities, which are categorized neither as held-to-maturity nor trading, net of adjustments including accretion, amortization, collection of cash, previous other-than-temporary impairments recognized in earnings (less any cumulative-effect adjustments recognized, as defined), and fair value hedge accounting adjustments, if any.

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