Income Taxes - Components of Net Deferred Tax Asset (Detail) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Deferred tax assets:
Bad debt and credit loss deduction	$ 22,402	$ 19,911
Net operating loss carryforward	141	207
Deferred compensation	6,109	5,501
PCI loans	2,556	3,098
California franchise tax	837	1,618
Accrued expense	4,865	1,365
Unrealized loss on investment securities, net	7,508	0
Acquired loan discounts	25,555	2,081
Other, net	2,624	1,272
Gross deferred tax asset	72,597	35,053
Deferred tax liabilities:
Depreciation	4,440	975
Intangibles—acquistions	19,843	3,404
FHLB stock	2,527	2,400
Deferred income	2,716	2,112
Unrealized gain on investment securities, net	0	775
Gross deferred tax liability	29,526	9,666
Net deferred tax asset	$ 43,071	$ 25,387