Age Analysis of Past Due Loans Segregated by Class of Loans (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-59 Days Past Due	$ 17,126	$ 19,664
60-89 Days Past Due	5,100	6,574
Greater Than 90 Days	18,079	31,838
Total Past Due	40,305	58,076
Current	950,264	862,133
Total Loans Receivable	990,569	920,209
Total Loans > 90 Days and Accruing	273	1,127
Commercial
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans Receivable	288,848	282,849
Commercial | Real estate
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-59 Days Past Due	1,097	870
60-89 Days Past Due	992	1,023
Greater Than 90 Days	2,350	7,592
Total Past Due	4,439	9,485
Current	199,174	187,905
Total Loans Receivable	203,613	197,390
Commercial | Construction and development
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-59 Days Past Due	192	845
Greater Than 90 Days	4,912	9,314
Total Past Due	5,104	10,159
Current	12,358	10,672
Total Loans Receivable	17,462	20,831
Commercial | Other
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-59 Days Past Due	259	791
60-89 Days Past Due	223	99
Greater Than 90 Days	735	1,160
Total Past Due	1,217	2,050
Current	66,556	62,578
Total Loans Receivable	67,773	64,628
Consumer loans
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Loans Receivable	199,102	202,384
Consumer loans | Real estate
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-59 Days Past Due	1,302	1,395
60-89 Days Past Due	358	1,167
Greater Than 90 Days	1,119	2,081
Total Past Due	2,779	4,643
Current	97,737	92,221
Total Loans Receivable	100,516	96,864
Consumer loans | Other
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-59 Days Past Due	234	227
60-89 Days Past Due	21	5
Greater Than 90 Days	95	89
Total Past Due	350	321
Current	6,248	6,439
Total Loans Receivable	6,598	6,760
Total Loans > 90 Days and Accruing	96
Consumer loans | Auto
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-59 Days Past Due	47	143
60-89 Days Past Due	18	28
Greater Than 90 Days	15	24
Total Past Due	80	195
Current	15,492	15,008
Total Loans Receivable	15,572	15,203
Consumer loans | Boat/RV
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-59 Days Past Due	1,508	2,084
60-89 Days Past Due	756	825
Greater Than 90 Days	497	371
Total Past Due	2,761	3,280
Current	73,655	80,277
Total Loans Receivable	76,416	83,557
Residential Mortgage
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-59 Days Past Due	12,487	13,309
60-89 Days Past Due	2,732	3,427
Greater Than 90 Days	8,356	11,207
Total Past Due	23,575	27,943
Current	479,044	407,033
Total Loans Receivable	502,619	434,976
Total Loans > 90 Days and Accruing	$ 177	$ 1,127