Loans - Non-Covered Loans Modified TDR (Detail) (Troubled Debt Restructurings Subsequently Defaulted [Member], USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012 Contract
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of Contracts	13
Recorded Investment	$ 3,366
Home equity [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of Contracts	2
Recorded Investment	222
Commercial real estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of Contracts	1
Recorded Investment	516
Residential mortgage [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of Contracts	10
Recorded Investment	$ 2,628