Loans Receivable, Net - Summary of the Activity in Loans Classified as TDRs (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Financing Receivable, Modifications [Line Items]
Beginning Balance	$ 3,163	$ 6,461
New TDR	431
Loss on Foreclosure	0	0
Transferred to Non-accrual	0	0
Loan Paid off	(64)
Loan Paid off		(3,298)
Ending Balance	3,530	3,163
Multi-Family [Member]
Financing Receivable, Modifications [Line Items]
Beginning Balance		815
Loss on Foreclosure		0
Transferred to Non-accrual		0
Loan Paid off		(815)
Non-Residential Real Estate [Member]
Financing Receivable, Modifications [Line Items]
Beginning Balance	3,163	5,646
New TDR	322
Loss on Foreclosure	0	0
Transferred to Non-accrual	0	0
Loan Paid off	(62)
Loan Paid off		(2,483)
Ending Balance	3,423	$ 3,163
Commercial Loans [Member]
Financing Receivable, Modifications [Line Items]
New TDR	109
Loss on Foreclosure	0
Transferred to Non-accrual	0
Loan Paid off	(2)
Ending Balance	$ 107