Annual report pursuant to Section 13 and 15(d)

Loans - Allowance for Loan Losses and Allowance for Off-Balance Sheet Items (Detail)

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Loans - Allowance for Loan Losses and Allowance for Off-Balance Sheet Items (Detail) (USD $)
12 Months Ended
Dec. 31, 2012
Dec. 31, 2011
Dec. 31, 2010
Allowance For Loan And Lease Losses [Line Items]      
Balance at Beginning of Period $ 22,587,000 $ 36,620,000  
Actual Charge-Offs (38,227,000) (78,652,000)  
Recoveries on Loans Previously Charged Off (4,439,000) (9,993,000)  
Balance at End of Period 8,306,000 22,587,000  
Allowance for Loan Losses [Member]
     
Allowance For Loan And Lease Losses [Line Items]      
Balance at Beginning of Period 89,936,000 146,059,000 144,996,000
Provision Charged to Operating Expense 7,157,000 12,536,000 122,955,000
Actual Charge-Offs (38,227,000) (78,652,000) (131,823,000)
Recoveries on Loans Previously Charged Off 4,439,000 9,993,000 9,931,000
Balance at End of Period 63,305,000 89,936,000 146,059,000
Allowance for Off-Balance Sheet Items [Member]
     
Allowance For Loan And Lease Losses [Line Items]      
Balance at Beginning of Period 2,981,000 3,417,000 3,876,000
Provision Charged to Operating Expense (1,157,000) (436,000) (459,000)
Actual Charge-Offs         
Recoveries on Loans Previously Charged Off         
Balance at End of Period $ 1,824,000 $ 2,981,000 $ 3,417,000