Loans Held for Investment - Schedule of Restructured Loans by Type, Net of Individually Evaluated Allowances (Details) $ in Thousands	3 Months Ended	12 Months Ended
	Sep. 30, 2021 USD ($) loan	Jun. 30, 2021 USD ($) loan
Financing Receivable, Impaired [Line Items]
Number of modified loans | loan	22	23
Restructured Loans, Allowance for Loan Losses	$ (260)	$ (384)
Restructured Loans, Unpaid Principal Balance	8,390	8,608
Restructured Loans, Related Charge-offs	(255)	(365)
Restructured Loans, Recorded Investment	8,135	8,243
Restructured loans, net investment	7,875	7,859
Mortgage loans, Single-family
Financing Receivable, Impaired [Line Items]
Restructured Loans, With Related Allowance, Unpaid Principal Balance	5,191	7,151
Restructured Loans, With Related Allowance, Related Charge-offs	0	0
Restructured Loans, With a Related Allowance, Recorded Investment	5,191	7,151
Restructured Loans, Allowance for Loan Losses	(260)	(384)
Restructured loans, with a related allowance, net investment	4,931	6,767
Restructured Loans, Without a Related Allowance, Unpaid Principal Balance	3,199	1,457
Restructured Loans, Without a Related Allowance, Related Charge-offs	(255)	(365)
Restructured Loans, Without a Related Allowance, Recorded Investment	2,944	1,092
Restructured Loans, Without a Related Allowance, Net Investment	2,944	1,092
Restructured Loans, Unpaid Principal Balance	8,390	8,608
Restructured Loans, Related Charge-offs	(255)	(365)
Restructured Loans, Recorded Investment	8,135	8,243
Restructured loans, net investment	$ 7,875	$ 7,859