Investment Securities - Gross Fair Value and Unrealized Losses (Detail) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012
Schedule of Available-for-sale Securities [Line Items]
Fair value less than twelve months	$ 49,576	$ 3,310
Unrealized losses less than twelve months	1,165	11
Fair value Twelve months or more	3,125	48
Unrealized losses Twelve months or more	20	2
Fair Value, Totals	52,701	3,358
Unrealized losses, Totals	1,185	13
U.S. Agency Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair value less than twelve months	41,214	3,169
Unrealized losses less than twelve months	439	2
Fair value Twelve months or more	3,125
Unrealized losses Twelve months or more	20
Fair Value, Totals	44,339	3,169
Unrealized losses, Totals	459	2
States & Political Subdivisions [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair value less than twelve months	8,362
Unrealized losses less than twelve months	726
Fair value Twelve months or more
Unrealized losses Twelve months or more
Fair Value, Totals	8,362
Unrealized losses, Totals	726
Equity Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair value less than twelve months		141
Unrealized losses less than twelve months		9
Fair value Twelve months or more		48
Unrealized losses Twelve months or more		2
Fair Value, Totals		189
Unrealized losses, Totals		$ 11