Loans - Activity in the allowance for loan losses by portfolio segment (Details) - USD ($)	3 Months Ended
Dec. 31, 2021	Sep. 30, 2021	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2021
Allowance for Loan and Lease Losses [Roll Forward]
Balance at beginning of year	$ 2,187,306	$ 2,186,182	$ 1,774,757	$ 1,699,977
Recoveries	1,337	1,124	342,954	74,780
Balance at end of year	2,188,643	2,187,306	2,117,711	1,774,757
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract]
Collectively evaluated for impairment	2,188,643		2,117,711		$ 2,186,182
Loans and Leases Receivable, Allowance	2,188,643	2,187,306	2,117,711	1,774,757	2,186,182
Loans - Individually evaluated for impairment	516,533		790,977		539,423
Loans - Collectively evaluated for impairment	158,066,006		124,644,766		146,334,172
Loans and Leases Receivable, Gross	158,582,539		125,435,743		146,873,595
Commercial real estate [Member] \| Commercial real estate
Allowance for Loan and Lease Losses [Roll Forward]
Balance at beginning of year	1,223,850	1,036,301	661,379	274,997
Provisions	64,577	187,549	280,505	386,382
Balance at end of year	1,288,427	1,223,850	941,884	661,379
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract]
Collectively evaluated for impairment	1,288,427		941,884		1,036,301
Loans and Leases Receivable, Allowance	1,288,427	1,223,850	941,884	661,379	1,036,301
Loans - Individually evaluated for impairment	217,449		230,331		223,983
Loans - Collectively evaluated for impairment	62,815,351		47,324,480		51,924,082
Loans and Leases Receivable, Gross	63,032,800		47,554,811		52,148,065
Commercial [Member] \| Commercial and industrial
Allowance for Loan and Lease Losses [Roll Forward]
Balance at beginning of year	68,497	157,533	113,232	1,021,083
Recoveries			341,388
Provisions	(19,488)	(89,036)	(344,174)	(907,851)
Balance at end of year	49,009	68,497	110,446	113,232
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract]
Collectively evaluated for impairment	49,009		110,446		157,533
Loans and Leases Receivable, Allowance	49,009	68,497	110,446	113,232	157,533
Loans - Collectively evaluated for impairment	8,901,181		11,017,967		19,278,477
Loans and Leases Receivable, Gross	8,901,181		11,017,967		19,278,477
Commercial [Member] \| Construction
Allowance for Loan and Lease Losses [Roll Forward]
Balance at beginning of year	50,646	59,649	127,596	43,858
Recoveries				73,128
Provisions	(2,866)	(9,003)	2,444	10,610
Balance at end of year	47,780	50,646	130,040	127,596
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract]
Collectively evaluated for impairment	47,780		130,040		59,649
Loans and Leases Receivable, Allowance	47,780	50,646	130,040	127,596	59,649
Loans - Collectively evaluated for impairment	8,098,343		10,080,584		7,985,188
Loans and Leases Receivable, Gross	8,098,343		10,080,584		7,985,188
Residential [Member] \| One-to-four-family residential
Allowance for Loan and Lease Losses [Roll Forward]
Balance at beginning of year	356,257	409,395	623,165	339,449
Provisions	(14,346)	(53,138)	(47,961)	283,716
Balance at end of year	341,911	356,257	575,204	623,165
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract]
Collectively evaluated for impairment	341,911		575,204		409,395
Loans and Leases Receivable, Allowance	341,911	356,257	575,204	623,165	409,395
Loans - Individually evaluated for impairment	299,084		470,318		315,440
Loans - Collectively evaluated for impairment	51,381,035		42,803,943		48,089,380
Loans and Leases Receivable, Gross	51,680,119		43,274,261		48,404,820
Residential [Member] \| Multi-family real estate
Allowance for Loan and Lease Losses [Roll Forward]
Balance at beginning of year	86,482	134,216	62,572	10,057
Provisions	34,871	(47,734)	23,163	52,515
Balance at end of year	121,353	86,482	85,735	62,572
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract]
Collectively evaluated for impairment	121,353		85,735		134,216
Loans and Leases Receivable, Allowance	121,353	86,482	85,735	62,572	134,216
Loans - Individually evaluated for impairment			90,328
Loans - Collectively evaluated for impairment	24,615,280		11,431,363		17,268,048
Loans and Leases Receivable, Gross	24,615,280		11,521,691		17,268,048
Consumer Loans [Member] \| Consumer
Allowance for Loan and Lease Losses [Roll Forward]
Balance at beginning of year	5,918	4,896	12,881	2,003
Recoveries	1,337	1,124	1,566	1,652
Provisions	(1,723)	(102)	(3,893)	9,226
Balance at end of year	5,532	5,918	10,554	12,881
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract]
Collectively evaluated for impairment	5,532		10,554		4,896
Loans and Leases Receivable, Allowance	5,532	5,918	10,554	12,881	4,896
Loans - Collectively evaluated for impairment	2,254,816		1,986,429		1,788,997
Loans and Leases Receivable, Gross	2,254,816		1,986,429		1,788,997
Unallocated
Allowance for Loan and Lease Losses [Roll Forward]
Balance at beginning of year	395,656	384,192	173,932	8,530
Provisions	(61,025)	11,464	89,916	165,402
Balance at end of year	334,631	395,656	263,848	173,932
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract]
Collectively evaluated for impairment	334,631		263,848		384,192
Loans and Leases Receivable, Allowance	$ 334,631	$ 395,656	$ 263,848	$ 173,932	$ 384,192

Amount of recovery of loans and lease receivables which had previously been fully or partially written-off as bad debts.

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The valuation allowance for financing receivables that are expected to be uncollectible that were collectively evaluated for impairment.

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The balance of financing receivables that were collectively evaluated for impairment.

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The balance of financing receivables that were individually evaluated for impairment.

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Amount of allowance to cover probable credit losses on loans and leases. Includes carryover of or adjustments to the allowance for loan losses in connection with business combinations. Excludes allowance for loans and leases covered under loss sharing agreements.

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Amount before allowance of loans and leases held in portfolio, including but not limited to, commercial and consumer loans. Includes deferred interest and fees, undisbursed portion of loan balance, unamortized costs and premiums and discounts from face amounts. Excludes loans and leases covered under loss sharing agreements.

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Amount of expense related to estimated loss from loan and lease transactions.

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