Loans - Non-Covered Loans Modified as TDR (Detail) (Troubled Debt Restructurings Subsequently Defaulted [Member], USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2014 Contract
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of Contracts	6
Recorded Investment	$ 3,529
Commercial and industrial [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of Contracts	2
Recorded Investment	2,132
Construction [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of Contracts	4
Recorded Investment	$ 1,397