Summary of Significant Accounting Policies - Significant events (Details)		3 Months Ended	6 Months Ended	12 Months Ended
	Mar. 27, 2020	Sep. 30, 2020 USD ($) loan	Sep. 30, 2020 USD ($) loan	Jun. 30, 2020 USD ($) loan	Sep. 30, 2019 USD ($)	Jun. 30, 2019 USD ($)
Financing Receivable, Impaired [Line Items]
Number of loans modification request received | loan		89	89
Aggregate value of requested loans to be modified		$ 28,000,000	$ 28,000,000
Modified loans requested and performing under Cares Act		$ 27,800,000	$ 27,800,000
Percentage of performing loans		99.10%
Number of loans resumed | loan		75	75
Modifications resumed		$ 21,206,401	$ 21,206,401
Number of loans in deferred status | loan		14	14
Modifications deferred		$ 6,792,416	$ 6,792,416
TDR's granted during the period | loan		1	2	1
TDR investment modified during the period		$ 47,853
TDR's outstanding		241,474	$ 241,474
Provision for loan losses				$ 135,000
Allowance for loan losses		$ 1,353,484	$ 1,353,484	$ 1,353,427	$ 1,286,674	$ 1,293,965
Percentage of allowance for loan losses on total loans		0.58%	0.58%	0.57%
Percentage of loan portfolio collateralized by real estate		98.60%	98.60%
Percentage of portfolio to borrowers in particularly hard-hit industries		1.60%	1.60%
PPP
Financing Receivable, Impaired [Line Items]
Percentage of loan proceeds used for payroll costs	75.00%
Percentage of loan proceeds used for other qualifying expenses	25.00%
Number of loan originated | loan		17
Value of loan		$ 1,100,000	$ 1,100,000
Processing fee income		$ 44,000
PPP | Minimum
Financing Receivable, Impaired [Line Items]
Processing fee income (as a percent)	1.00%
Third party service fee payable (as a percent)	0.25%
PPP | Maximum
Financing Receivable, Impaired [Line Items]
Processing fee income (as a percent)	5.00%
Third party service fee payable (as a percent)	1.00%