Newly Restructured Loans by Type (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011
Residential Mortgage
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total modification		$ 733
Consumer loans | Other
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total modification		48
Newly restructured loans | Commercial | Real estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Interest Only		885
Term	1,281	494
Combination	1,118	508
Total modification	2,399	1,887
Newly restructured loans | Commercial | Construction and Land Development
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term	961	4,146
Combination	172
Total modification	1,133	4,146
Newly restructured loans | Commercial | Other
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term	143	293
Combination	243	103
Total modification	386	396
Newly restructured loans | Residential Mortgage
Accounts, Notes, Loans and Financing Receivable [Line Items]
Interest Only	320	1,471
Term	961	11
Combination	2,432	1,538
Total modification	3,713	3,020
Newly restructured loans | Consumer loans | Real estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term	117	133
Combination	858	721
Total modification	975	854
Newly restructured loans | Consumer loans | Other
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term	8	3
Combination	44
Total modification	52	3
Newly restructured loans | Consumer loans | Auto
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term	29	10
Combination	4
Total modification	33	10
Newly restructured loans | Consumer loans | Boat/RV
Accounts, Notes, Loans and Financing Receivable [Line Items]
Interest Only		75
Term	153	208
Combination		93
Total modification	$ 153	$ 376