Investment Securities - Schedule of Gross Unrealized Losses and Fair Value (Detail) $ in Thousands	Dec. 31, 2021 USD ($) Security	Sep. 30, 2021 USD ($) Security
Schedule of Available-for-sale Securities [Line Items]
Number of Securities, Debt | Security	98	69
Fair Value, Less than Twelve Months, Debt	$ 89,285	$ 52,675
Gross Unrealized Losses, Less than Twelve Months, Debt	(1,315)	(689)
Fair Value, Twelve Months or Greater, Debt	9,698	10,401
Gross Unrealized Losses, Twelve Months or Greater, Debt	(204)	(199)
Fair Value Total, Debt	98,983	63,076
Gross Unrealized Losses Total, Debt	$ (1,519)	$ (888)
Fannie Mae [Member]
Schedule of Available-for-sale Securities [Line Items]
Number of Securities, Debt | Security	24	17
Fair Value, Less than Twelve Months, Debt	$ 30,474	$ 15,410
Gross Unrealized Losses, Less than Twelve Months, Debt	(278)	(127)
Fair Value, Twelve Months or Greater, Debt	3,705	4,078
Gross Unrealized Losses, Twelve Months or Greater, Debt	(17)	(14)
Fair Value Total, Debt	34,179	19,488
Gross Unrealized Losses Total, Debt	$ (295)	$ (141)
Freddie Mac [Member]
Schedule of Available-for-sale Securities [Line Items]
Number of Securities, Debt | Security	19	12
Fair Value, Less than Twelve Months, Debt	$ 26,525	$ 14,466
Gross Unrealized Losses, Less than Twelve Months, Debt	(212)	(165)
Fair Value Total, Debt	26,525	14,466
Gross Unrealized Losses Total, Debt	$ (212)	$ (165)
Governmental National Mortgage Association [Member]
Schedule of Available-for-sale Securities [Line Items]
Number of Securities, Debt | Security	8	4
Fair Value, Less than Twelve Months, Debt	$ 954
Gross Unrealized Losses, Less than Twelve Months, Debt	(4)
Fair Value, Twelve Months or Greater, Debt	1,803	$ 2,038
Gross Unrealized Losses, Twelve Months or Greater, Debt	(13)	(14)
Fair Value Total, Debt	2,757	2,038
Gross Unrealized Losses Total, Debt	$ (17)	$ (14)
Corporate Obligations [Member]
Schedule of Available-for-sale Securities [Line Items]
Number of Securities, Debt | Security	38	28
Fair Value, Less than Twelve Months, Debt	$ 31,331	$ 22,799
Gross Unrealized Losses, Less than Twelve Months, Debt	(821)	(397)
Fair Value, Twelve Months or Greater, Debt	1,931	1,937
Gross Unrealized Losses, Twelve Months or Greater, Debt	(63)	(56)
Fair Value Total, Debt	33,262	24,736
Gross Unrealized Losses Total, Debt	$ (884)	$ (453)
Other Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Number of Securities, Debt | Security	9	8
Fair Value, Less than Twelve Months, Debt	$ 1
Fair Value, Twelve Months or Greater, Debt	2,259	$ 2,348
Gross Unrealized Losses, Twelve Months or Greater, Debt	(111)	(115)
Fair Value Total, Debt	2,260	2,348
Gross Unrealized Losses Total, Debt	$ (111)	$ (115)