Securities Available-for-Sale - Fair Value and Age of Gross Unrealized Losses by Investment Category (Detail) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2014 security	Dec. 31, 2013 security
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale, Securities, Less Than 12 Months, Number of Positions	5	41
Available-for-sale Securities, Less Than 12 Months, Fair Value	$ 41,434	$ 274,942
Available-for-sale Securities, Less Than 12 Months, Unrealized Losses	(313)	(6,913)
Available-for-sale, Securities, 12 Months or More, Number of Positions	14	2
Available-for-sale Securities, 12 Months or More, Fair Value	109,491	10,088
Available-for-sale Securities, 12 Months or More, Unrealized Losses	(1,989)	(863)
Available-for-sale Securities, Fair Value, Total	150,925	285,030
Number of debt securities on which unrealized losses were primarily attributable to changes in interest	19
Available-for-sale, Securities, Number of Positions		43
Available-for-sale Securities, Unrealized Losses, Total	(2,302)	(7,776)
Obligations of U.S. Government Corporations and Agencies [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale, Securities, Less Than 12 Months, Number of Positions	2	16
Available-for-sale Securities, Less Than 12 Months, Fair Value	19,741	126,017
Available-for-sale Securities, Less Than 12 Months, Unrealized Losses	(78)	(2,581)
Available-for-sale, Securities, 12 Months or More, Number of Positions	8	0
Available-for-sale Securities, 12 Months or More, Fair Value	63,265	0
Available-for-sale Securities, 12 Months or More, Unrealized Losses	(1,021)	0
Available-for-sale Securities, Fair Value, Total	83,006	126,017
Available-for-sale, Securities, Number of Positions	10	16
Available-for-sale Securities, Unrealized Losses, Total	(1,099)	(2,581)
Collateralized Mortgage Obligations of U.S. Government Corporations and Agencies [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale, Securities, Less Than 12 Months, Number of Positions	1	3
Available-for-sale Securities, Less Than 12 Months, Fair Value	11,420	39,522
Available-for-sale Securities, Less Than 12 Months, Unrealized Losses	(218)	(603)
Available-for-sale, Securities, 12 Months or More, Number of Positions	0	0
Available-for-sale Securities, 12 Months or More, Fair Value	0	0
Available-for-sale Securities, 12 Months or More, Unrealized Losses	0	0
Available-for-sale Securities, Fair Value, Total	11,420	39,522
Available-for-sale, Securities, Number of Positions	1	3
Available-for-sale Securities, Unrealized Losses, Total	(218)	(603)
Residential Mortgage-Backed Securities of U.S. Government Corporations and Agencies [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale, Securities, Less Than 12 Months, Number of Positions	0	2
Available-for-sale Securities, Less Than 12 Months, Fair Value	0	22,822
Available-for-sale Securities, Less Than 12 Months, Unrealized Losses	0	(685)
Available-for-sale, Securities, 12 Months or More, Number of Positions	1	0
Available-for-sale Securities, 12 Months or More, Fair Value	9,414	0
Available-for-sale Securities, 12 Months or More, Unrealized Losses	(231)	0
Available-for-sale Securities, Fair Value, Total	9,414	22,822
Available-for-sale, Securities, Number of Positions	1	2
Available-for-sale Securities, Unrealized Losses, Total	(231)	(685)
Commercial Mortgage-Backed Securities of U.S. Government Corporations and Agencies [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale, Securities, Less Than 12 Months, Number of Positions	1	4
Available-for-sale Securities, Less Than 12 Months, Fair Value	10,009	39,052
Available-for-sale Securities, Less Than 12 Months, Unrealized Losses	(16)	(1,305)
Available-for-sale, Securities, 12 Months or More, Number of Positions	2	0
Available-for-sale Securities, 12 Months or More, Fair Value	20,837	0
Available-for-sale Securities, 12 Months or More, Unrealized Losses	(386)	0
Available-for-sale Securities, Fair Value, Total	30,846	39,052
Available-for-sale, Securities, Number of Positions	3	4
Available-for-sale Securities, Unrealized Losses, Total	(402)	(1,305)
Obligations of States and Political Subdivisions [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale, Securities, Less Than 12 Months, Number of Positions	1	16
Available-for-sale Securities, Less Than 12 Months, Fair Value	264	47,529
Available-for-sale Securities, Less Than 12 Months, Unrealized Losses	(1)	(1,739)
Available-for-sale, Securities, 12 Months or More, Number of Positions	3	2
Available-for-sale Securities, 12 Months or More, Fair Value	15,975	10,088
Available-for-sale Securities, 12 Months or More, Unrealized Losses	(351)	(863)
Available-for-sale Securities, Fair Value, Total	16,239	57,617
Available-for-sale, Securities, Number of Positions	4	18
Available-for-sale Securities, Unrealized Losses, Total	(352)	(2,602)
Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale, Securities, Less Than 12 Months, Number of Positions	5	41
Available-for-sale Securities, Less Than 12 Months, Fair Value	41,434	274,942
Available-for-sale Securities, Less Than 12 Months, Unrealized Losses	(313)	(6,913)
Available-for-sale, Securities, 12 Months or More, Number of Positions	14	2
Available-for-sale Securities, 12 Months or More, Fair Value	109,491	10,088
Available-for-sale Securities, 12 Months or More, Unrealized Losses	(1,989)	(863)
Available-for-sale Securities, Fair Value, Total	150,925	285,030
Available-for-sale, Securities, Number of Positions	19	43
Available-for-sale Securities, Unrealized Losses, Total	(2,302)	(7,776)
Marketable Equity Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale, Securities, Less Than 12 Months, Number of Positions	0	0
Available-for-sale Securities, Less Than 12 Months, Fair Value	0	0
Available-for-sale Securities, Less Than 12 Months, Unrealized Losses	0	0
Available-for-sale, Securities, 12 Months or More, Number of Positions	0	0
Available-for-sale Securities, 12 Months or More, Fair Value	0	0
Available-for-sale Securities, 12 Months or More, Unrealized Losses	0	0
Available-for-sale Securities, Fair Value, Total	0	0
Available-for-sale, Securities, Number of Positions	0	0
Available-for-sale Securities, Unrealized Losses, Total	$ 0	$ 0