Loans, Leases and Allowance for Credit Losses - Interest Income on Impaired Loans by Loan Class (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Financing Receivable, Impaired [Line Items]
Total interest income on impaired loans by class	$ 1,113	$ 1,182
Owner occupied [Member] | Commercial real estate [Member]
Financing Receivable, Impaired [Line Items]
Total interest income on impaired loans by class	295	420
Non-owner occupied [Member] | Commercial real estate [Member]
Financing Receivable, Impaired [Line Items]
Total interest income on impaired loans by class	338	330
Multi-family [Member] | Commercial real estate [Member]
Financing Receivable, Impaired [Line Items]
Total interest income on impaired loans by class	0	0
Commercial [Member] | Commercial and industrial [Member]
Financing Receivable, Impaired [Line Items]
Total interest income on impaired loans by class	108	79
Leases [Member] | Commercial and industrial [Member]
Financing Receivable, Impaired [Line Items]
Total interest income on impaired loans by class	32	0
Construction [Member] | Construction and land development [Member]
Financing Receivable, Impaired [Line Items]
Total interest income on impaired loans by class	0	0
Land [Member] | Construction and land development [Member]
Financing Receivable, Impaired [Line Items]
Total interest income on impaired loans by class	207	194
Residential real estate [Member]
Financing Receivable, Impaired [Line Items]
Total interest income on impaired loans by class	131	157
Consumer [Member]
Financing Receivable, Impaired [Line Items]
Total interest income on impaired loans by class	$ 2	$ 2