Investment Securities - Gross Unrealized Losses on Investment (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2013
Schedule of Available-for-sale Securities [Line Items]
Less than 12 months, Fair Value	$ 10,486
Less than 12 months, Unrealized Loss	(358)
12 months or more, Fair Value
12 months or more, Unrealized Loss
Total Fair Value	10,486
Total Unrealized Loss	(358)
Less than 12 months, Fair Value, Held to Maturity	199,403
Less than 12 months, Unrealized Loss, Held to Maturity	(6,995)
12 months or more, Fair Value, Held to Maturity
12 months or more, Unrealized Loss, Held to Maturity
Total Fair Value, Held to Maturity	199,403
Total Unrealized Loss, Held to Maturity	(6,995)
Obligations of U.S. government corporations and agencies [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than 12 months, Fair Value	10,287
Less than 12 months, Unrealized Loss	(357)
12 months or more, Fair Value
12 months or more, Unrealized Loss
Total Fair Value	10,287
Total Unrealized Loss	(357)
Less than 12 months, Fair Value, Held to Maturity	188,218
Less than 12 months, Unrealized Loss, Held to Maturity	(5,540)
12 months or more, Fair Value, Held to Maturity
12 months or more, Unrealized Loss, Held to Maturity
Total Fair Value, Held to Maturity	188,218
Total Unrealized Loss, Held to Maturity	(5,540)
Obligations of states and political subdivisions [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than 12 months, Fair Value	199
Less than 12 months, Unrealized Loss	(1)
12 months or more, Fair Value
12 months or more, Unrealized Loss
Total Fair Value	199
Total Unrealized Loss	(1)
Less than 12 months, Fair Value, Held to Maturity	11,185
Less than 12 months, Unrealized Loss, Held to Maturity	(1,455)
12 months or more, Fair Value, Held to Maturity
12 months or more, Unrealized Loss, Held to Maturity
Total Fair Value, Held to Maturity	11,185
Total Unrealized Loss, Held to Maturity	(1,455)
Corporate debt securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than 12 months, Fair Value
Less than 12 months, Unrealized Loss
12 months or more, Fair Value
12 months or more, Unrealized Loss
Total Fair Value
Total Unrealized Loss
Less than 12 months, Fair Value, Held to Maturity
Less than 12 months, Unrealized Loss, Held to Maturity
12 months or more, Fair Value, Held to Maturity
12 months or more, Unrealized Loss, Held to Maturity
Total Fair Value, Held to Maturity
Total Unrealized Loss, Held to Maturity