Assets and Liabilities Measured at Fair Value on Non-Recurring Basis (Detail) (Fair Value, Measurements, Nonrecurring, 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]
Certain impaired loans	$ 82,451		$ 72,582
Other assets	42,978	[1]	26,810	[1]
Total	125,429		99,392
Significant Other Observable Inputs (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other assets	42,978	[1]	26,810	[1]
Total	42,978		26,810
Significant Unobservable Inputs (Level 3)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Certain impaired loans	82,451		72,582
Total	$ 82,451		$ 72,582

[1] Represents the fair value of OREO that was measured at fair value, based on the appraised value of the collateral, subsequent to its initial classification as OREO.