Premises and Equipment - Schedule of Future Minimum Operating Lease Payments (Detail) $ in Thousands	Dec. 31, 2017 USD ($)
Property Plant And Equipment Capitalized Interest Costs [Abstract]
Due in one year or less	$ 653
Due after one year through two years	252
Due after two years through three years	173
Due after three years through four years	139
Due after four years through five years	141
Thereafter	2,741
Total	$ 4,099