Fair Value Measurement of Assets and Liabilities - Additional Information (Detail) (USD $)	3 Months Ended	6 Months Ended
	Jun. 30, 2013	Jun. 30, 2013
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Fair value, unobservable inputs, quantitative information for assets measured on non-recurring basis, impaired loans non-current appraisal discount percentage		13.80%
Impaired collateral dependent loans, charge-offs	$ 5,200,000	$ 13,400,000
Collateral dependent impaired loans, recorded investment	49,500,000	49,500,000
Specific valuation allowance allocations	7,700,000	7,700,000
Reported net carrying amount of impaired loans	41,800,000	41,800,000
Foreclosed assets measured at fair value upon initial recognition	7,200,000	7,200,000
Allowance for loan losses, charge-offs	1,600,000	3,100,000
Loss due to re-measurement of repossessed assets		570,000
Loan servicing rights [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Valuation of loan servicing rights, discount rate		8.00%
Net recoveries of impairment charges	$ 759,000	$ 2,100,000
Loan servicing rights [Member] | Minimum [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Valuation of loan servicing rights, prepayment rate		6.00%
Loan servicing rights [Member] | Maximum [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Valuation of loan servicing rights, prepayment rate		24.00%