Activity in Allowance for Losses for Non-Covered Loans and Covered Loans (Detail) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2012	Dec. 31, 2011
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for Loan Losses, Individually evaluated for impairment	$ 3,540	$ 490
Allowance for Loan Losses, Collectively evaluated for impairment	134,374	136,800
Allowance for Loan Losses, Acquired loans with deteriorated credit quality	51,771	33,323
Allowance for Loan Losses	189,685	170,613
Mortgage Receivable
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for Loan Losses, Individually evaluated for impairment	3,540	490
Allowance for Loan Losses, Collectively evaluated for impairment	120,754	121,505
Allowance for Loan Losses, Acquired loans with deteriorated credit quality	30,804	14,227
Allowance for Loan Losses	155,098	136,222
Other loan
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for Loan Losses, Collectively evaluated for impairment	13,620	15,295
Allowance for Loan Losses, Acquired loans with deteriorated credit quality	20,967	19,096
Allowance for Loan Losses	$ 34,587	$ 34,391