Information Regarding Troubled Debt Restructurings (Detail) - Non-Covered Loans - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Financing Receivable, Modifications [Line Items]
Troubled debt restructurings	$ 46,389	$ 45,556
Multi-Family
Financing Receivable, Modifications [Line Items]
Troubled debt restructurings	8,427	8,885
Commercial Real Estate
Financing Receivable, Modifications [Line Items]
Troubled debt restructurings	365	368
One-to-four family
Financing Receivable, Modifications [Line Items]
Troubled debt restructurings	1,053	1,066
Acquisition, Development and Construction
Financing Receivable, Modifications [Line Items]
Troubled debt restructurings	9,552	8,652
Commercial and Industrial
Financing Receivable, Modifications [Line Items]
Troubled debt restructurings	26,992	26,585
Accruing
Financing Receivable, Modifications [Line Items]
Troubled debt restructurings	10,372	9,653
Accruing | Multi-Family
Financing Receivable, Modifications [Line Items]
Troubled debt restructurings	820	824
Accruing | Acquisition, Development and Construction
Financing Receivable, Modifications [Line Items]
Troubled debt restructurings	9,552	8,652
Accruing | Commercial and Industrial
Financing Receivable, Modifications [Line Items]
Troubled debt restructurings		177
Non-Accrual
Financing Receivable, Modifications [Line Items]
Troubled debt restructurings	36,017	35,903
Non-Accrual | Multi-Family
Financing Receivable, Modifications [Line Items]
Troubled debt restructurings	7,607	8,061
Non-Accrual | Commercial Real Estate
Financing Receivable, Modifications [Line Items]
Troubled debt restructurings	365	368
Non-Accrual | One-to-four family
Financing Receivable, Modifications [Line Items]
Troubled debt restructurings	1,053	1,066
Non-Accrual | Commercial and Industrial
Financing Receivable, Modifications [Line Items]
Troubled debt restructurings	$ 26,992	$ 26,408