Foreclosed Assets - Summary of Activity in Balance of Foreclosed Assets (Detail) $ in Thousands	3 Months Ended
	Mar. 31, 2018 USD ($) Assets	Mar. 31, 2017 USD ($) Assets
Schedule Of Foreclosed Assets Activity [Line Items]
Beginning balance, net	$ 3,226	$ 3,986
Additions/transfers from loans		85
Dispositions/sales	(1,572)	(608)
Valuation adjustments	(90)	66
Ending balance, net	1,564	3,529
Ending valuation allowance	$ (152)	$ (300)
Ending number of foreclosed assets | Assets	10	12
Proceeds from sale of foreclosed assets	$ 1,943	$ 726
Gain (loss) on sale of foreclosed assets	$ 371	118
Noncovered [Member]
Schedule Of Foreclosed Assets Activity [Line Items]
Beginning balance, net		3,763
Additions/transfers from loans		85
Dispositions/sales		(385)
Valuation adjustments		66
Ending balance, net		3,529
Ending valuation allowance		$ (300)
Ending number of foreclosed assets | Assets		12
Proceeds from sale of foreclosed assets		$ 510
Gain (loss) on sale of foreclosed assets		125
Covered [Member]
Schedule Of Foreclosed Assets Activity [Line Items]
Beginning balance, net		223
Dispositions/sales		(223)
Proceeds from sale of foreclosed assets		216
Gain (loss) on sale of foreclosed assets		$ (7)