Loans and Leases - Summary of Non-Performing Assets (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Accounts, Notes, Loans and Financing Receivable [Line Items]
Troubled debt restructurings	$ 53,991	$ 46,933
Non-Performing
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-accrual loans	74,635	65,479
Troubled debt restructurings	23,481	20,428
Total non-performing loans	98,116	85,907
Other real estate owned (OREO)	40,606	32,490
Total non-performing assets	$ 138,722	$ 118,397
Non-performing loans / total loans and leases	0.47%	0.58%
Non-performing loans OREO / total loans and leases OREO	0.66%	0.79%
Non-performing assets / total assets	0.44%	0.54%