Loans, Allowance for Loan Losses, and Credit Quality Indicators - Schedule of Past Due Payments (Detail)	12 Months Ended
	Dec. 31, 2012
Financing Receivable, Recorded Investment, Past Due [Line Items]
2 Payments	30 Days
3 Payments	60 Days
4 Payments	90 Days
5 Payments	120 Days
6 Payments	150 Days
7 Payments	180 Days