Loans - Summary of Carrying Balance of Troubled Debt Restructurings at Dates (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Financing Receivable, Modifications [Line Items]
Total troubled debt restructurings	$ 33,278	$ 55,103
Other Loans Held for Sale [Member]
Financing Receivable, Modifications [Line Items]
Total troubled debt restructurings	33,278	46,737
Loans, Gross [Member]
Financing Receivable, Modifications [Line Items]
Total troubled debt restructurings		8,366
Performing [Member]
Financing Receivable, Modifications [Line Items]
Total troubled debt restructurings	30,154	45,557
Performing [Member] | Other Loans Held for Sale [Member]
Financing Receivable, Modifications [Line Items]
Total troubled debt restructurings	30,154	37,191
Performing [Member] | Loans, Gross [Member]
Financing Receivable, Modifications [Line Items]
Total troubled debt restructurings		8,366
Nonperforming [Member]
Financing Receivable, Modifications [Line Items]
Total troubled debt restructurings	3,124	9,546
Nonperforming [Member] | Other Loans Held for Sale [Member]
Financing Receivable, Modifications [Line Items]
Total troubled debt restructurings	$ 3,124	$ 9,546