Allowance for Credit Losses - Provision for Credit Losses (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Receivables [Abstract]
Provision for loan losses	$ 3,710	$ 1,363	$ 6,112	$ 2,092
Provision for unfunded letters of credit	(78)	66	(10)	137
Total provision for credit losses	$ 3,632	$ 1,429	$ 6,102	$ 2,229