Covered Loans Acquired in AmTrust and Desert Hills Acquisitions (Detail) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2011	Dec. 31, 2010
Accounts, Notes, Loans and Financing Receivable [Line Items]
Covered loans	$ 3,873,294	$ 4,297,869
Percent of Covered Loans	100.00%
One- to Four-Family
Accounts, Notes, Loans and Financing Receivable [Line Items]
Covered loans	3,503,673
Percent of Covered Loans	90.50%
Other loan
Accounts, Notes, Loans and Financing Receivable [Line Items]
Covered loans	$ 369,621
Percent of Covered Loans	9.50%