Allowance for Loan Losses - Analysis of Allowance for Loan Losses (Detail) - USD ($) $ in Thousands	3 Months Ended					12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Receivables [Abstract]
Allowance for loan losses, beginning of year				$ 23,075	$ 22,318	$ 23,075	$ 22,318	$ 20,941
Loans charged-off						(389)	(781)	(1,382)
Recoveries on loans previously charged-off						434	1,338	709
Net recoveries (charge-offs)						45	557	(673)
Provision charged to expense	$ 200	$ 375	$ 350	$ 450	$ 200	1,375	200	2,050
Reclassification to other liabilities						(89)
Allowance for loan losses, end of year	$ 24,406					$ 24,406	$ 23,075	$ 22,318