Loans and Allowance for Credit Losses - Credit risk profile based on rating and payment activity (Details) - USD ($)	3 Months Ended	12 Months Ended
	Sep. 30, 2021	Jun. 30, 2021
Pass
Financing Receivable, Credit Quality Indicator [Line Items]
PCD loans receivable, net of ACL	$ 12,100,000	$ 3,200,000
Watch
Financing Receivable, Credit Quality Indicator [Line Items]
PCD loans receivable, net of ACL	0	9,000,000.0
Special Mention
Financing Receivable, Credit Quality Indicator [Line Items]
PCD loans receivable, net of ACL	0	0
Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
PCD loans receivable, net of ACL	2,800,000	2,700,000
Doubtful
Financing Receivable, Credit Quality Indicator [Line Items]
PCD loans receivable, net of ACL	$ 0	$ 0