Deposits - Summary of Scheduled Maturities of Time Deposits (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Banking And Thrift [Abstract]
Due in one year or less	$ 503,803
Due after one year through two years	123,235
Due after two years through three years	58,090
Due after three years through four years	33,171
Due after four years through five years	56,886
Thereafter	1,314
Total	$ 776,499	$ 553,158