Information Regarding Troubled Debt Restructurings (Detail) - Non-Covered Loans - USD ($) $ in Thousands		Sep. 30, 2019	Dec. 31, 2018
Financing Receivable, Modifications [Line Items]
Troubled debt restructurings		$ 43,333	$ 34,881
Multi-Family
Financing Receivable, Modifications [Line Items]
Troubled debt restructurings		3,741	4,220
Commercial Real Estate
Financing Receivable, Modifications [Line Items]
Troubled debt restructurings		0	0
One-to-four family
Financing Receivable, Modifications [Line Items]
Troubled debt restructurings		891	1,022
Acquisition, development, and construction
Financing Receivable, Modifications [Line Items]
Troubled debt restructurings		2,349	8,297
Commercial and Industrial
Financing Receivable, Modifications [Line Items]
Troubled debt restructurings	[1]	36,352	21,342
Accruing
Financing Receivable, Modifications [Line Items]
Troubled debt restructurings		3,214	9,162
Accruing | Multi-Family
Financing Receivable, Modifications [Line Items]
Troubled debt restructurings		0	0
Accruing | Commercial Real Estate
Financing Receivable, Modifications [Line Items]
Troubled debt restructurings		0	0
Accruing | One-to-four family
Financing Receivable, Modifications [Line Items]
Troubled debt restructurings		0	0
Accruing | Acquisition, development, and construction
Financing Receivable, Modifications [Line Items]
Troubled debt restructurings		2,349	8,297
Accruing | Commercial and Industrial
Financing Receivable, Modifications [Line Items]
Troubled debt restructurings	[1]	865	865
Non-Accrual
Financing Receivable, Modifications [Line Items]
Troubled debt restructurings		40,119	25,719
Non-Accrual | Multi-Family
Financing Receivable, Modifications [Line Items]
Troubled debt restructurings		3,741	4,220
Non-Accrual | Commercial Real Estate
Financing Receivable, Modifications [Line Items]
Troubled debt restructurings		0	0
Non-Accrual | One-to-four family
Financing Receivable, Modifications [Line Items]
Troubled debt restructurings		891	1,022
Non-Accrual | Acquisition, development, and construction
Financing Receivable, Modifications [Line Items]
Troubled debt restructurings		0	0
Non-Accrual | Commercial and Industrial
Financing Receivable, Modifications [Line Items]
Troubled debt restructurings	[1]	$ 35,487	$ 20,477

[1] Includes $27.4 million and $20.4 million of taxi medallion-related loans at September 30, 2019 and December 31, 2018, respectively.