Recurring Basis (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012
Commercial and Industrial Loans and Leases [Member] | Minimum [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
(Weighted Average)	4.00%
Commercial and Industrial Loans and Leases [Member] | Maximum [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
(Weighted Average)	68.00%
Commercial Real Estate Loans [Member] | Minimum [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
(Weighted Average)	15.00%
Commercial Real Estate Loans [Member] | Maximum [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
(Weighted Average)	78.00%
Impaired Loans with Specific Allocations [Member] | Significant Unobservable Inputs (Level 3) [Member] | Commercial and Industrial Loans and Leases [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	$ 1,231
Valuation Technique(s)	Sales comparison approach
Unobservable Input(s)	Adjustment for differences between the comparable sales
Impaired Loans with Specific Allocations [Member] | Significant Unobservable Inputs (Level 3) [Member] | Commercial and Industrial Loans and Leases [Member] | Weighted Average [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
(Weighted Average)	8.00%
Impaired Loans with Specific Allocations [Member] | Significant Unobservable Inputs (Level 3) [Member] | Commercial Real Estate Loans [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	1,497
Valuation Technique(s)	Sales comparison approach Income approach Cost approach
Unobservable Input(s)	Adjustment for physical condition of comparable properties sold Adjustment for net operating income generated by the property Adjustment for investor rates of return
Impaired Loans with Specific Allocations [Member] | Significant Unobservable Inputs (Level 3) [Member] | Commercial Real Estate Loans [Member] | Weighted Average [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
(Weighted Average)	48.00%
Impaired Loans with Specific Allocations [Member] | Significant Unobservable Inputs (Level 3) [Member] | Agricultural Loans [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	$ 135
Valuation Technique(s)	Sales comparison approach Income approach
Unobservable Input(s)	Adjustment for physical condition of comparable properties sold Adjustment for net operating income generated by the property
(Weighted Average)	76.00%
Impaired Loans with Specific Allocations [Member] | Significant Unobservable Inputs (Level 3) [Member] | Agricultural Loans [Member] | Weighted Average [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
(Weighted Average)	76.00%