Covered Loans Acquired in AmTrust and Desert Hills Acquisitions (Detail) - USD ($) $ in Thousands	Sep. 30, 2016	Dec. 31, 2015
Accounts, Notes, Loans and Financing Receivable [Line Items]
Covered loans	$ 1,789,164	$ 2,060,089
Percent of Covered Loans	100.00%
One-to-four family
Accounts, Notes, Loans and Financing Receivable [Line Items]
Covered loans	$ 1,688,148
Percent of Covered Loans	94.40%
Other loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Covered loans	$ 101,016
Percent of Covered Loans	5.60%