Fair Value - Additional Information (Detail) (USD $)	3 Months Ended		12 Months Ended
	Mar. 31, 2015	Mar. 31, 2014	Dec. 31, 2014
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Accretion of discounts on securities included in interest income	$ 5,000	$ 5,000
Provision for loan losses expensed	4,800,000		5,400,000
Net carrying amount other real estate owned and other repossessed property			6,400,000
Other real estate owned property write-downs	1,100,000		2,600,000
Past due period of mortgage loans held for sale, days	90 days
Interest income for residential loans held for sale	39,000	43,000
Valuation Allowance, Real Estate Owned [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Net carrying amount other real estate owned and other repossessed property	5,200,000
Impaired Commercial and Commercial Real Estate Loans [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Principal amount of impaired commercial and commercial real estate loans	29,700,000		30,000,000
Valuation allowance	$ 11,800,000		$ 10,200,000