Loans Receivable, Net and Allowance for Credit Losses on Loans - Amortized Cost Basis of Loans on Nonaccrual Status and Loans Past Due Over 90 Days and Still Accruing (Detail) - USD ($) $ in Thousands	Mar. 31, 2025	Sep. 30, 2024
Financing Receivable, Nonaccrual [Line Items]
Nonaccrual with No ACL	$ 7,992	$ 9,026
Nonaccrual with ACL	81
Total Nonaccrual	8,073	9,026
Total Nonperforming	8,073	9,026
Home Equity Loans and Lines of Credit [Member]
Financing Receivable, Nonaccrual [Line Items]
Nonaccrual with No ACL	28	35
Total Nonaccrual	28	35
Total Nonperforming	28	35
Auto [Member]
Financing Receivable, Nonaccrual [Line Items]
Nonaccrual with No ACL		1
Total Nonaccrual		1
Total Nonperforming		1
Other [Member]
Financing Receivable, Nonaccrual [Line Items]
Nonaccrual with No ACL	21	23
Total Nonaccrual	21	23
Total Nonperforming	21	23
Residential [Member] \| Real Estate Loans [Member]
Financing Receivable, Nonaccrual [Line Items]
Nonaccrual with No ACL	1,843	1,955
Total Nonaccrual	1,843	1,955
Total Nonperforming	1,843	1,955
Commercial [Member] \| Real Estate Loans [Member]
Financing Receivable, Nonaccrual [Line Items]
Nonaccrual with No ACL	5,499	5,876
Nonaccrual with ACL	81
Total Nonaccrual	5,580	5,876
Total Nonperforming	5,580	5,876
Commercial Portfolio Segment [Member]
Financing Receivable, Nonaccrual [Line Items]
Nonaccrual with No ACL	601	1,136
Total Nonaccrual	601	1,136
Total Nonperforming	$ 601	$ 1,136

ESSA Bancorp, Inc. 10-Q