Activity in Allowance for Losses for Non-Covered Loans (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Valuation Allowance [Line Items]
Balance, end of year	$ 137,290	$ 158,942
Non-Covered Loans
Valuation Allowance [Line Items]
Balance, beginning of year	158,942	127,491	94,368
Provision for loan losses	79,000	91,000	63,000
Charge-offs	(105,910)	(60,785)	(29,931)
Recoveries	5,258	1,236	54
Balance, end of year	$ 137,290	$ 158,942	$ 127,491