Loans and Leases - Summary of Non-Performing Assets (Detail) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2015	Dec. 31, 2014
Accounts, Notes, Loans and Financing Receivable [Line Items]
Troubled debt restructurings	$ 42,855	$ 41,152
Non-Performing [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-accrual loans	45,029	45,113
Troubled debt restructurings	22,022	23,439
Total non-performing loans	67,051	68,552
Other real estate owned (OREO)	40,796	41,466
Total non-performing assets	$ 107,847	$ 110,018
Non-performing loans as a percent of total loans and leases	0.59%	0.61%
Non-performing loans + OREO as a percent of total loans and leases + OREO	0.94%	0.97%
Non-performing assets as a percent of total assets	0.66%	0.68%