Deposits (Detail) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2018	Dec. 31, 2017
Banking and Thrift [Abstract]
Percentage Change, Checking, non-interest bearing	(2.20%)
Percentage Change, Checking, interest bearing	6.90%
Percentage Change, Savings accounts	20.60%
Percentage Change, Certificates of deposit	3.50%
Percentage change, Total	10.80%
Checking, non-interest bearing	$ 314,906	$ 321,858
Checking, interest bearing	604,326	565,399
Savings accounts	1,104,563	915,587
Certificates of deposit	377,770	364,971
Total deposits	$ 2,401,565	$ 2,167,815