Investment Securities - Gross Unrealized Losses and Fair Value for Investment Securities by Investment Category and Continuous Unrealized Loss Position Time (Detail) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2014	Dec. 31, 2013
Schedule of Available-for-sale Securities [Line Items]
Less than Twelve Months, Fair Value	$ 112,428	$ 131,410
Less than Twelve Months, Gross Unrealized Losses	(3,409)	(5,074)
Twelve Months or Greater, Fair Value	13,631	13,607
Twelve Months or Greater, Gross Unrealized Losses	(656)	(827)
Total Fair Value	126,059	145,017
Total Gross Unrealized Losses	(4,065)	(5,901)
U.S. Government Corporations and Agencies [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than Twelve Months, Fair Value	44,110	46,416
Less than Twelve Months, Gross Unrealized Losses	(1,480)	(2,170)
Twelve Months or Greater, Fair Value
Twelve Months or Greater, Gross Unrealized Losses
Total Fair Value	44,110	46,416
Total Gross Unrealized Losses	(1,480)	(2,170)
States and Political Subdivisions [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than Twelve Months, Fair Value	9,986	19,009
Less than Twelve Months, Gross Unrealized Losses	(370)	(867)
Twelve Months or Greater, Fair Value	2,013	1,794
Twelve Months or Greater, Gross Unrealized Losses	(143)	(189)
Total Fair Value	11,999	20,803
Total Gross Unrealized Losses	(513)	(1,056)
Mortgage-backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than Twelve Months, Fair Value	58,262	65,915
Less than Twelve Months, Gross Unrealized Losses	(1,558)	(2,036)
Twelve Months or Greater, Fair Value	11,618	11,805
Twelve Months or Greater, Gross Unrealized Losses	(513)	(637)
Total Fair Value	69,880	77,720
Total Gross Unrealized Losses	(2,071)	(2,673)
Total Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than Twelve Months, Fair Value	112,358	131,340
Less than Twelve Months, Gross Unrealized Losses	(3,408)	(5,073)
Twelve Months or Greater, Fair Value	13,631	13,599
Twelve Months or Greater, Gross Unrealized Losses	(656)	(826)
Total Fair Value	125,989	144,939
Total Gross Unrealized Losses	(4,064)	(5,899)
Equity Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than Twelve Months, Fair Value	70	70
Less than Twelve Months, Gross Unrealized Losses	(1)	(1)
Twelve Months or Greater, Fair Value		8
Twelve Months or Greater, Gross Unrealized Losses		(1)
Total Fair Value	70	78
Total Gross Unrealized Losses	$ (1)	$ (2)