Non-Covered Loans Modified TDR (Detail) (Troubled Debt Restructurings Subsequently Defaulted, USD $) In Thousands, unless otherwise specified	3 Months Ended	9 Months Ended
	Sep. 30, 2012 Contract	Sep. 30, 2012 Contract
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of Contracts	1	4
Recorded Investment	$ 2,767	$ 2,767
Commercial and Industrial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of Contracts	1	2
Recorded Investment	1,616	1,616
Commercial Real Estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of Contracts		1
Recorded Investment	1,093	1,093
Residential Mortgage
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of Contracts		1
Recorded Investment	$ 58	$ 58