Investment Securities - Amortized Cost and Estimated Fair Value of Held-to-Maturity Securities and Available-for-Sale Securities by Contractual Maturity (Detail) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2014	Dec. 31, 2013
Schedule of Available for Sale and Held To Maturity Securities [Line Items]
Securities Held-to-Maturity, Amortized Cost	$ 56,604	$ 66,003
Securities Held-to-Maturity, Fair Value	57,499	66,853
Amortized Cost, Total	299,220	338,546
Gross Unrealized Gains, Total	4,332	2,883
Gross Unrealized Losses, Total	(1,696)	(5,148)
Fair Value, Total	301,856	336,281
Equity Securities [Member]
Schedule of Available for Sale and Held To Maturity Securities [Line Items]
Securities Available-for-Sale, Amortized Cost, Total	854	1,679
Securities Available-for-Sale, Amortized Cost, No stated maturity	854	1,679
Securities Available-for-Sale, Gross Unrealized Gains, No stated maturity	453	668
Securities Available-for-Sale, Gross Unrealized Losses, No stated maturity
Securities Available-for-Sale, Fair Value, No stated maturity	1,307	2,347
Gross Unrealized Gains, Total	453	668
Securities Available-for-Sale, Fair Value, Total	1,307	2,347
U.S. Treasuries [Member]
Schedule of Available for Sale and Held To Maturity Securities [Line Items]
Securities Available-for-Sale, Amortized Cost After 5 years to 10 years	4,969	4,966
Securities Available-for-Sale, Gross Unrealized Losses After 5 years to 10 years	(161)	(258)
Securities Available-for-Sale, Fair Value After 5 years to 10 years	4,808	4,708
Amortized Cost, Total	4,969	4,966
Gross Unrealized Losses, Total	(161)	(258)
Securities Available-for-Sale, Fair Value, Total	4,808	4,708
U.S. Government Corporations and Agencies [Member]
Schedule of Available for Sale and Held To Maturity Securities [Line Items]
Securities Available-for-Sale, Amortized Cost Within 1 year		5,999
Securities Available-for-Sale, Gross Unrealized Gains Within 1 year		16
Securities Available-for-Sale, Gross Unrealized Losses Within 1 year
Securities Available-for-Sale, Fair Value Within 1 year		6,015
Securities Available-for-Sale, Amortized Cost After 1 year to 5 years	112,614	112,989
Securities Available-for-Sale, Gross Unrealized Gains After 1 year to 5 years	130	114
Securities Available-for-Sale, Gross Unrealized Losses After 1 year to 5 years	(413)	(1,226)
Securities Available-for-Sale, Fair Value After 1 year to 5 years	112,331	111,877
Securities Available-for-Sale, Amortized Cost After 5 years to 10 years	10,747	10,816
Securities Available-for-Sale, Gross Unrealized Losses After 5 years to 10 years	(196)	(560)
Securities Available-for-Sale, Fair Value After 5 years to 10 years	10,551	10,256
Amortized Cost, Total	123,361	129,804
Gross Unrealized Gains, Total	130	130
Gross Unrealized Losses, Total	(609)	(1,786)
Securities Available-for-Sale, Fair Value, Total	122,882	128,148
State and Political Subdivisions [Member]
Schedule of Available for Sale and Held To Maturity Securities [Line Items]
Securities Available-for-Sale, Amortized Cost Within 1 year	600	1,564
Securities Available-for-Sale, Gross Unrealized Gains Within 1 year	2	13
Securities Available-for-Sale, Gross Unrealized Losses Within 1 year
Securities Available-for-Sale, Fair Value Within 1 year	602	1,577
Securities Available-for-Sale, Amortized Cost After 1 year to 5 years	9,407	5,305
Securities Available-for-Sale, Gross Unrealized Gains After 1 year to 5 years	26	14
Securities Available-for-Sale, Gross Unrealized Losses After 1 year to 5 years	(20)	(29)
Securities Available-for-Sale, Fair Value After 1 year to 5 years	9,413	5,290
Securities Available-for-Sale, Amortized Cost After 5 years to 10 years	46,951	41,974
Securities Available-for-Sale, Gross Unrealized Gains After 5 years to 10 years	1,458	710
Securities Available-for-Sale, Gross Unrealized Losses After 5 years to 10 years	(150)	(698)
Securities Available-for-Sale, Fair Value After 5 years to 10 years	48,259	41,986
Securities Available-for-Sale, Amortized Cost Over 10 years	47,081	57,899
Securities Available-for-Sale, Gross Unrealized Gains Over 10 years	2,068	1,227
Securities Available-for-Sale, Gross Unrealized Losses Over 10 years	(59)	(322)
Securities Available-for-Sale, Fair Value Over 10 years	49,090	58,804
Amortized Cost, Total	104,039	106,742
Gross Unrealized Gains, Total	3,554	1,964
Gross Unrealized Losses, Total	(229)	(1,049)
Securities Available-for-Sale, Fair Value, Total	107,364	107,657
Residential Mortgage-Backed Securities [Member]
Schedule of Available for Sale and Held To Maturity Securities [Line Items]
Securities Available-for-Sale, Amortized Cost After 5 years to 10 years	9,977	10,008
Securities Available-for-Sale, Gross Unrealized Gains After 5 years to 10 years		5
Securities Available-for-Sale, Gross Unrealized Losses After 5 years to 10 years	(143)	(53)
Securities Available-for-Sale, Fair Value After 5 years to 10 years	9,834	9,960
Securities Available-for-Sale, Amortized Cost Over 10 years	2,280	25,721
Securities Available-for-Sale, Gross Unrealized Gains Over 10 years	55	20
Securities Available-for-Sale, Gross Unrealized Losses Over 10 years		(221)
Securities Available-for-Sale, Fair Value Over 10 years	2,335	25,520
Amortized Cost, Total	12,257	35,729
Gross Unrealized Gains, Total	55	25
Gross Unrealized Losses, Total	(143)	(274)
Securities Available-for-Sale, Fair Value, Total	12,169	35,480
Collateralized Mortgage Obligations [Member]
Schedule of Available for Sale and Held To Maturity Securities [Line Items]
Securities Available-for-Sale, Amortized Cost After 1 year to 5 years	8	73
Securities Available-for-Sale, Fair Value After 1 year to 5 years	8	73
Securities Available-for-Sale, Amortized Cost Over 10 years	6,851	7,341
Securities Available-for-Sale, Gross Unrealized Gains Over 10 years	41	40
Securities Available-for-Sale, Gross Unrealized Losses Over 10 years	(197)	(253)
Securities Available-for-Sale, Fair Value Over 10 years	6,695	7,128
Amortized Cost, Total	6,859	7,414
Gross Unrealized Gains, Total	41	40
Gross Unrealized Losses, Total	(197)	(253)
Securities Available-for-Sale, Fair Value, Total	6,703	7,201
Corporate Bonds [Member]
Schedule of Available for Sale and Held To Maturity Securities [Line Items]
Securities Held-to-Maturity, Amortized Cost Within 1 year	13,160	11,148
Securities Held-to-Maturity, Gross Unrealized Gains Within 1 year	240	122
Securities Held-to-Maturity, Fair Value Within 1 year	13,400	11,270
Securities Held-to-Maturity, Amortized Cost After 1 year to 5 years	43,444	54,855
Securities Held-to-Maturity, Gross Unrealized Gains After 1 year to 5 years	680	992
Securities Held-to-Maturity, Gross Unrealized Losses After 1 year to 5 years	(25)	(264)
Securities Held-to-Maturity, Fair Value After 1 year to 5 years	44,099	55,583
Securities Held-to-Maturity, Amortized Cost	56,604	66,003
Securities Held-to-Maturity, Gross Unrealized Gains	920	1,114
Securities Held-to-Maturity, Gross Unrealized Losses	(25)	(264)
Securities Held-to-Maturity, Fair Value	57,499	66,853
Securities Available-for-Sale, Amortized Cost After 1 year to 5 years	21,920	18,838
Securities Available-for-Sale, Gross Unrealized Gains After 1 year to 5 years	92	52
Securities Available-for-Sale, Gross Unrealized Losses After 1 year to 5 years	(137)	(411)
Securities Available-for-Sale, Fair Value After 1 year to 5 years	21,875	18,479
Securities Available-for-Sale, Amortized Cost After 5 years to 10 years	20,950	16,474
Securities Available-for-Sale, Gross Unrealized Gains After 5 years to 10 years	7	4
Securities Available-for-Sale, Gross Unrealized Losses After 5 years to 10 years	(220)	(1,117)
Securities Available-for-Sale, Fair Value After 5 years to 10 years	20,737	15,361
Amortized Cost, Total	42,870	35,312
Gross Unrealized Gains, Total	99	56
Gross Unrealized Losses, Total	(357)	(1,528)
Securities Available-for-Sale, Fair Value, Total	42,612	33,840
Money Market Mutual Funds [Member]
Schedule of Available for Sale and Held To Maturity Securities [Line Items]
Securities Available-for-Sale, Amortized Cost, No stated maturity	4,011	16,900
Securities Available-for-Sale, Gross Unrealized Losses, No stated maturity
Securities Available-for-Sale, Fair Value, No stated maturity	4,011	16,900
Amortized Cost, Total	4,011	16,900
Securities Available-for-Sale, Fair Value, Total	$ 4,011	$ 16,900