Fair Value - Schedule of Financial Assets Measured at Fair Value on Nonrecurring Basis (Detail) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2012	Dec. 31, 2011
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Collateral dependent impaired loans	$ 77,259	$ 55,252
Other real estate owned	130,046	144,367
Total nonrecurring fair value measurements	207,305	199,619
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Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Collateral dependent impaired loans	77,259	55,252
Other real estate owned	130,046	144,367
Total nonrecurring fair value measurements	$ 207,305	$ 199,619