Non-Covered Loans Modified TDR (Detail) (Troubled Debt Restructurings Subsequently Defaulted, USD $) In Thousands, unless otherwise specified	3 Months Ended	6 Months Ended
	Jun. 30, 2012	Jun. 30, 2012
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of Contracts	2	5
Recorded Investment	$ 321	$ 2,397
Commercial and Industrial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of Contracts		1
Recorded Investment		646
Commercial Real Estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of Contracts		1
Recorded Investment		1,108
Residential Mortgage
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of Contracts	2	3
Recorded Investment	$ 321	$ 643