Investments - Summary of Amortized Cost and Estimated Fair Value of Fixed Maturities and Equity Securities (Detail) (USD $)	Sep. 30, 2014	Dec. 31, 2013	Nov. 30, 2013
Schedule of Equity Method Investments [Line Items]
Total held to maturity, Amortized Cost	$ 308,941,155	$ 240,370,277
Held to Maturity, Gross Unrealized Gains	11,682,000	515,000
Held to Maturity, Gross Unrealized Losses	641,000	2,095,000
Total held to maturity, Estimated Fair Value	319,982,000	238,790,000	212,228,289
Available for Sale, Amortized Cost	440,783,000	402,422,000
Available for Sale, Gross Unrealized Gains	21,611,000	13,943,000
Available for Sale, Gross Unrealized Losses	686,000	290,000
Available for Sale, Estimated Fair Value	461,708,000	416,075,000
U.S. Treasury Securities and Obligations of U.S. Government Corporations and Agencies [Member]
Schedule of Equity Method Investments [Line Items]
Total held to maturity, Amortized Cost	53,509,000	47,946,000
Held to Maturity, Gross Unrealized Gains	870,000
Held to Maturity, Gross Unrealized Losses	27,000	870,000
Total held to maturity, Estimated Fair Value	54,352,000	47,076,000	47,914,311
Available for Sale, Amortized Cost	18,887,000	14,272,000
Available for Sale, Gross Unrealized Gains	95,000	118,000
Available for Sale, Gross Unrealized Losses	43,000	57,000
Available for Sale, Estimated Fair Value	18,939,000	14,333,000
Obligations of States and Political Subdivisions [Member]
Schedule of Equity Method Investments [Line Items]
Total held to maturity, Amortized Cost	108,931,000	108,435,000
Held to Maturity, Gross Unrealized Gains	9,067,000	465,000
Held to Maturity, Gross Unrealized Losses	42,000	446,000
Total held to maturity, Estimated Fair Value	117,956,000	108,454,000	79,866,801
Available for Sale, Amortized Cost	248,645,000	265,783,000
Available for Sale, Gross Unrealized Gains	18,329,000	11,779,000
Available for Sale, Gross Unrealized Losses		15,000
Available for Sale, Estimated Fair Value	266,974,000	277,547,000
Corporate Securities [Member]
Schedule of Equity Method Investments [Line Items]
Total held to maturity, Amortized Cost	52,171,000	14,875,000
Held to Maturity, Gross Unrealized Gains	779,000	17,000
Held to Maturity, Gross Unrealized Losses	227,000	112,000
Total held to maturity, Estimated Fair Value	52,723,000	14,780,000	14,879,294
Available for Sale, Amortized Cost	58,209,000	39,940,000
Available for Sale, Gross Unrealized Gains	967,000	775,000
Available for Sale, Gross Unrealized Losses	41,000	43,000
Available for Sale, Estimated Fair Value	59,135,000	40,672,000
Mortgage-Backed Securities [Member]
Schedule of Equity Method Investments [Line Items]
Total held to maturity, Amortized Cost	94,330,000	69,114,000
Held to Maturity, Gross Unrealized Gains	966,000	33,000
Held to Maturity, Gross Unrealized Losses	345,000	667,000
Total held to maturity, Estimated Fair Value	94,951,000	68,480,000	69,567,883
Available for Sale, Amortized Cost	85,254,000	70,259,000
Available for Sale, Gross Unrealized Gains	1,475,000	923,000
Available for Sale, Gross Unrealized Losses	156,000	82,000
Available for Sale, Estimated Fair Value	86,573,000	71,100,000
Fixed Maturities [Member]
Schedule of Equity Method Investments [Line Items]
Available for Sale, Amortized Cost	410,995,000	390,254,000
Available for Sale, Gross Unrealized Gains	20,866,000	13,595,000
Available for Sale, Gross Unrealized Losses	240,000	197,000
Available for Sale, Estimated Fair Value	431,621,000	403,652,000
Equity Securities [Member]
Schedule of Equity Method Investments [Line Items]
Available for Sale, Amortized Cost	29,788,000	12,168,000
Available for Sale, Gross Unrealized Gains	745,000	348,000
Available for Sale, Gross Unrealized Losses	446,000	93,000
Available for Sale, Estimated Fair Value	$ 30,087,000	$ 12,423,000