Commitments and Letters of Credit - Additional Information (Detail) (USD $)	Dec. 31, 2014	Dec. 31, 2013
Loss Contingencies [Line Items]
Notional amount of financial standby letters of credit	$ 300,000
Notional amount of performance standby letters of credit	1,900,000
Notional amount of commercial letters of credit	232,000
Financial instrument of credit risk	200,000	100,000
Unused commitments and letters of credit [Member]
Loss Contingencies [Line Items]
Commitment liability	$ 3,100,000	$ 3,200,000