Fair Value Measurements - Schedule of Assets and Liabilities Measured at Fair Value on Recurring Basis (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012
Fair Value Measurements Disclosure [Line Items]
Securities available for sale/Available-for-sale, Fair value	$ 257,770	$ 155,905
Equity securities [Member]
Fair Value Measurements Disclosure [Line Items]
Securities available for sale/Available-for-sale, Fair value	9,302	6,766
Fair Value, Measurements, Recurring [Member]
Fair Value Measurements Disclosure [Line Items]
Securities available for sale/Available-for-sale, Fair value	257,770	155,905
Fair Value, Measurements, Recurring [Member] | Other Investment [Member]
Fair Value Measurements Disclosure [Line Items]
Securities available for sale/Available-for-sale, Fair value	10,591
Fair Value, Measurements, Recurring [Member] | Equity securities [Member] | Common Stock
Fair Value Measurements Disclosure [Line Items]
Securities available for sale/Available-for-sale, Fair value	9,302	6,766
Fair Value, Measurements, Recurring [Member] | Debt Securities [Member]
Fair Value Measurements Disclosure [Line Items]
Securities available for sale/Available-for-sale, Fair value	237,877	149,139
Fair Value, Measurements, Recurring [Member] | Debt Securities [Member] | States and political subdivisions [Member]
Fair Value Measurements Disclosure [Line Items]
Securities available for sale/Available-for-sale, Fair value	150,375	98,242
Fair Value, Measurements, Recurring [Member] | Debt Securities [Member] | U.S. agency-based mortgage-backed securities [Member]
Fair Value Measurements Disclosure [Line Items]
Securities available for sale/Available-for-sale, Fair value	7,074	11,087
Fair Value, Measurements, Recurring [Member] | Debt Securities [Member] | Corporate bonds [Member]
Fair Value Measurements Disclosure [Line Items]
Securities available for sale/Available-for-sale, Fair value	80,428	39,810
Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value Measurements Disclosure [Line Items]
Securities available for sale/Available-for-sale, Fair value	9,302	6,766
Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Other Investment [Member]
Fair Value Measurements Disclosure [Line Items]
Securities available for sale/Available-for-sale, Fair value
Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Equity securities [Member] | Common Stock
Fair Value Measurements Disclosure [Line Items]
Securities available for sale/Available-for-sale, Fair value	9,302	6,766
Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Debt Securities [Member]
Fair Value Measurements Disclosure [Line Items]
Securities available for sale/Available-for-sale, Fair value
Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Debt Securities [Member] | States and political subdivisions [Member]
Fair Value Measurements Disclosure [Line Items]
Securities available for sale/Available-for-sale, Fair value
Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Debt Securities [Member] | U.S. agency-based mortgage-backed securities [Member]
Fair Value Measurements Disclosure [Line Items]
Securities available for sale/Available-for-sale, Fair value
Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Debt Securities [Member] | Corporate bonds [Member]
Fair Value Measurements Disclosure [Line Items]
Securities available for sale/Available-for-sale, Fair value
Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value Measurements Disclosure [Line Items]
Securities available for sale/Available-for-sale, Fair value	237,877	149,139
Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Other Investment [Member]
Fair Value Measurements Disclosure [Line Items]
Securities available for sale/Available-for-sale, Fair value
Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Equity securities [Member] | Common Stock
Fair Value Measurements Disclosure [Line Items]
Securities available for sale/Available-for-sale, Fair value
Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Debt Securities [Member]
Fair Value Measurements Disclosure [Line Items]
Securities available for sale/Available-for-sale, Fair value	237,877	149,139
Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Debt Securities [Member] | States and political subdivisions [Member]
Fair Value Measurements Disclosure [Line Items]
Securities available for sale/Available-for-sale, Fair value	150,375	98,242
Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Debt Securities [Member] | U.S. agency-based mortgage-backed securities [Member]
Fair Value Measurements Disclosure [Line Items]
Securities available for sale/Available-for-sale, Fair value	7,074	11,087
Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Debt Securities [Member] | Corporate bonds [Member]
Fair Value Measurements Disclosure [Line Items]
Securities available for sale/Available-for-sale, Fair value	80,428	39,810
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value Measurements Disclosure [Line Items]
Securities available for sale/Available-for-sale, Fair value	10,591
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Other Investment [Member]
Fair Value Measurements Disclosure [Line Items]
Securities available for sale/Available-for-sale, Fair value	10,591
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Equity securities [Member] | Common Stock
Fair Value Measurements Disclosure [Line Items]
Securities available for sale/Available-for-sale, Fair value
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Debt Securities [Member]
Fair Value Measurements Disclosure [Line Items]
Securities available for sale/Available-for-sale, Fair value
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Debt Securities [Member] | States and political subdivisions [Member]
Fair Value Measurements Disclosure [Line Items]
Securities available for sale/Available-for-sale, Fair value
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Debt Securities [Member] | U.S. agency-based mortgage-backed securities [Member]
Fair Value Measurements Disclosure [Line Items]
Securities available for sale/Available-for-sale, Fair value
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Debt Securities [Member] | Corporate bonds [Member]
Fair Value Measurements Disclosure [Line Items]
Securities available for sale/Available-for-sale, Fair value