Securities - Amortized Cost of Securities and their Estimated Fair Values (Detail) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$ 336,268	$ 340,488
Gross Unrealized Gains	7,868	16,628
Gross Unrealized Losses	(5,200)	(771)
Estimated Fair Value	338,936	356,345
FHLB Stock [Member] | Restricted [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	4,428	4,428
Estimated Fair Value	4,428	4,428
Agency Debt Securities [Member] | Unrestricted [Member] | US Government and Agency Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	119,837	147,659
Gross Unrealized Gains	3,007	5,202
Gross Unrealized Losses	(1,427)	(83)
Estimated Fair Value	121,417	152,778
Corporate Bonds [Member] | Unrestricted [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	2,000
Gross Unrealized Losses	(16)
Estimated Fair Value	1,984
Taxable Municipals Bonds [Member] | Unrestricted [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	19,395	12,535
Gross Unrealized Gains	339	1,209
Gross Unrealized Losses	(334)	(8)
Estimated Fair Value	19,400	13,736
Tax Free Municipals Bonds [Member] | Unrestricted [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	65,395	68,331
Gross Unrealized Gains	2,550	5,756
Gross Unrealized Losses	(772)	(40)
Estimated Fair Value	67,173	74,047
Trust Preferred Securities [Member] | Unrestricted [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	2,000	2,000
Gross Unrealized Gains
Gross Unrealized Losses	(511)	(511)
Estimated Fair Value	1,489	1,489
GNMA [Member] | Mortgage-Backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	20,167	19,172
Gross Unrealized Gains	768	1,244
Gross Unrealized Losses	(117)	(19)
Estimated Fair Value	20,818	20,397
FNMA [Member] | Mortgage-Backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	77,307	64,805
Gross Unrealized Gains	927	2,558
Gross Unrealized Losses	(1,369)	(58)
Estimated Fair Value	76,865	67,305
FHLMC [Member] | Mortgage-Backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	3,441	4,519
Gross Unrealized Gains	88	153
Gross Unrealized Losses
Estimated Fair Value	3,529	4,672
Non-Agency CMOs [Member] | Mortgage-Backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	13,931	5,412
Gross Unrealized Gains		80
Gross Unrealized Losses	(487)
Estimated Fair Value	13,444	5,492
Agency CMOs [Member] | Mortgage-Backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	12,795	16,055
Gross Unrealized Gains	189	426
Gross Unrealized Losses	(167)	(52)
Estimated Fair Value	$ 12,817	$ 16,429