Commitments and Letters of Credit - Additional Information (Detail) - USD ($)	Dec. 31, 2016	Dec. 31, 2015
Loss Contingencies [Line Items]
Notional amount of financial standby letters of credit	$ 400,000
Notional amount of performance standby letters of credit	3,000,000
Notional amount of commercial letters of credit	201,000
Financial instrument of credit risk	165,000	$ 200,000
Unused commitments and letters of credit [Member]
Loss Contingencies [Line Items]
Commitment liability	$ 4,100,000	$ 4,400,000