Newly Restructured Loans by Type (Detail) (Newly restructured loans, USD $) In Thousands, unless otherwise specified	3 Months Ended	9 Months Ended
	Sep. 30, 2012	Sep. 30, 2012
Commercial | Real estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term		$ 403
Combination	439	1,117
Total modification	439	1,520
Commercial | Construction and Land Development
Accounts, Notes, Loans and Financing Receivable [Line Items]
Combination	172	172
Total modification	172	172
Commercial | Other
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term	46	143
Combination		181
Total modification	46	324
Residential Mortgage
Accounts, Notes, Loans and Financing Receivable [Line Items]
Interest Only		320
Term	36	169
Combination	698	2,107
Total modification	734	2,596
Consumer loans | Real estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term	22	55
Combination	416	775
Total modification	438	830
Consumer loans | Other
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term		8
Combination	36	44
Total modification	36	52
Consumer loans | Auto
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term	4	11
Combination	4	4
Total modification	8	15
Consumer loans | Boat/RV
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term	95	153
Total modification	$ 95	$ 153