CONSOLIDATED STATEMENTS OF FINANCIAL CONDITION (Parenthetical) - USD ($) $ in Thousands	Mar. 31, 2021	Sep. 30, 2020
Statement Of Financial Position [Abstract]
Investment securities available for sale, amortized cost	$ 29,165	$ 31,658
Investment securities held to maturity, fair value	26,367	15,608
Allowance for loan losses	$ 12,601	$ 12,433
Preferred stock, par value (in dollars per share)	$ 0.01	$ 0.01
Preferred stock, authorized	10,000,000	10,000,000
Preferred stock, shares issued	0	0
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common stock, authorized	50,000,000	50,000,000
Common stock, issued	7,804,469	7,804,469
Common stock, outstanding	7,609,953	7,609,953
Treasury stock, shares	194,516	194,516