Loans, Leases and Allowance for Credit Losses - Impaired Loans by Loan Class (Detail) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Financing Receivable, Impaired [Line Items]
Total impaired loans by class	$ 128,874	$ 166,750
Residential real estate [Member]
Financing Receivable, Impaired [Line Items]
Total impaired loans by class	16,575	19,300
Consumer [Member]
Financing Receivable, Impaired [Line Items]
Total impaired loans by class	334	363
Commercial real estate [Member] | Owner occupied [Member]
Financing Receivable, Impaired [Line Items]
Total impaired loans by class	23,153	44,893
Commercial real estate [Member] | Non-owner occupied [Member]
Financing Receivable, Impaired [Line Items]
Total impaired loans by class	41,081	66,324
Commercial real estate [Member] | Multi-family [Member]
Financing Receivable, Impaired [Line Items]
Total impaired loans by class	0	0
Commercial and industrial [Member]
Financing Receivable, Impaired [Line Items]
Total impaired loans by class	26,513	13,749
Commercial and industrial [Member] | Commercial [Member]
Financing Receivable, Impaired [Line Items]
Total impaired loans by class	26,513	13,749
Commercial and industrial [Member] | Leases [Member]
Financing Receivable, Impaired [Line Items]
Total impaired loans by class	2,896	373
Construction and land development [Member] | Construction [Member]
Financing Receivable, Impaired [Line Items]
Total impaired loans by class	0	0
Construction and land development [Member] | Land [Member]
Financing Receivable, Impaired [Line Items]
Total impaired loans by class	$ 18,322	$ 21,748