Deposits - Total Deposits (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Dec. 31, 2017
Banking and Thrift [Abstract]
Percentage Change, Checking, non-interest bearing	(3.40%)
Percentage Change, Checking, interest bearing	4.70%
Percentage Change, Savings accounts	1.60%
Percentage Change, Certificates of deposit	3.20%
Percentage change, Total	1.90%
Checking, non-interest bearing	$ 311,052	$ 321,858
Checking, interest bearing	592,075	565,399
Savings accounts	930,108	915,587
Certificates of deposit	376,820	364,971
Total deposits	$ 2,210,055	$ 2,167,815