Loans and Leases - Summary of Non-Performing Assets (Detail) - USD ($) $ in Thousands	Sep. 30, 2015	Dec. 31, 2014
Accounts, Notes, Loans and Financing Receivable [Line Items]
Troubled debt restructurings	$ 43,713	$ 41,152
Non-Performing [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-accrual loans	47,298	45,113
Troubled debt restructurings	21,221	23,439
Total non-performing loans	68,519	68,552
Other real estate owned (OREO)	38,931	41,466
Total non-performing assets	$ 107,450	$ 110,018
Non-performing loans as a percent of total loans and leases	0.58%	0.61%
Non-performing loans + OREO as a percent of total loans and leases + OREO	0.90%	0.97%
Non-performing assets as a percent of total assets	0.64%	0.68%