Information Regarding Troubled Debt Restructurings (Detail) - Non-Covered Loans - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Financing Receivable, Modifications [Line Items]
Troubled debt restructurings	$ 45,556	$ 19,920
Multi-Family
Financing Receivable, Modifications [Line Items]
Troubled debt restructurings	8,885	10,736
Commercial Real Estate
Financing Receivable, Modifications [Line Items]
Troubled debt restructurings	368	1,861
One-to-four family
Financing Receivable, Modifications [Line Items]
Troubled debt restructurings	1,066	1,971
Acquisition, Development and Construction
Financing Receivable, Modifications [Line Items]
Troubled debt restructurings	8,652
Commercial and Industrial
Financing Receivable, Modifications [Line Items]
Troubled debt restructurings	26,585	5,150
Other loans
Financing Receivable, Modifications [Line Items]
Troubled debt restructurings		202
Accruing
Financing Receivable, Modifications [Line Items]
Troubled debt restructurings	9,653	3,466
Accruing | Multi-Family
Financing Receivable, Modifications [Line Items]
Troubled debt restructurings	824	1,981
Accruing | One-to-four family
Financing Receivable, Modifications [Line Items]
Troubled debt restructurings		222
Accruing | Acquisition, Development and Construction
Financing Receivable, Modifications [Line Items]
Troubled debt restructurings	8,652
Accruing | Commercial and Industrial
Financing Receivable, Modifications [Line Items]
Troubled debt restructurings	177	1,263
Non-Accrual
Financing Receivable, Modifications [Line Items]
Troubled debt restructurings	35,903	16,454
Non-Accrual | Multi-Family
Financing Receivable, Modifications [Line Items]
Troubled debt restructurings	8,061	8,755
Non-Accrual | Commercial Real Estate
Financing Receivable, Modifications [Line Items]
Troubled debt restructurings	368	1,861
Non-Accrual | One-to-four family
Financing Receivable, Modifications [Line Items]
Troubled debt restructurings	1,066	1,749
Non-Accrual | Commercial and Industrial
Financing Receivable, Modifications [Line Items]
Troubled debt restructurings	$ 26,408	3,887
Non-Accrual | Other loans
Financing Receivable, Modifications [Line Items]
Troubled debt restructurings		$ 202