Summary of Significant Accounting Policies - Narrative (Details) $ / shares in Units, $ in Thousands			12 Months Ended
	Nov. 11, 2022 USD ($) $ / shares	Feb. 08, 2021 $ / shares shares	Sep. 30, 2022 USD ($) payment segment branch	Sep. 30, 2021 USD ($)	Sep. 30, 2020 USD ($)	Dec. 31, 2021 USD ($)	Oct. 27, 2020 USD ($)	Oct. 09, 2013 USD ($)
Summary of Significant Accounting Policies [Line Items]
Number of offices | branch			201
Dividend rate		4.875%
Proceeds from issuance of preferred stock, net			$ 0	$ 293,325	$ 0
Cash collateral			284,400	$ 1,500
Fair value of NAV			41,476
Remaining unfunded commitment			$ 7,511
Days past grace period to initiate contact to cure deficiency			30 days
Minimum days past due to begin foreclosure proceedings			90 days
Approximate rate reduction concession, minimum			1.00%
Approximate rate reduction concession, maximum			2.00%
Minimum days past due to stop accrual of interest			90 days
Loans returned to full accrual status			90 days
Number of payments required | payment			6
Options exercisable, weighted average remaining contractual term (in years)			6 years
Number of reportable business segments | segment			1
Civil money penalty from consent order issued						$ 2,500	$ 200	$ 34
Subsequent Event
Summary of Significant Accounting Policies [Line Items]
Common stock transaction value	$ 654,000
Number of shares issued in transaction, price per share (in dollars per share) | $ / shares	$ 0.3353
Public Offering
Summary of Significant Accounting Policies [Line Items]
Number of shares issued in transaction (in shares) | shares		12,000,000
Percentage of preferred stock		2.50%
Public offering price (in usd per share) | $ / shares		$ 25.00
Series A Preferred Stock | Public Offering
Summary of Significant Accounting Policies [Line Items]
Number of shares issued in transaction (in shares) | shares		300,000
Minimum
Summary of Significant Accounting Policies [Line Items]
Term for payment and rate reduction			6 months
Award vesting period (in years)			3 years
Maximum
Summary of Significant Accounting Policies [Line Items]
Term for payment and rate reduction			12 months
Award vesting period (in years)			5 years
Options exercisable, weighted average remaining contractual term (in years)			10 years
Stock Options and Restricted Stock | Minimum
Summary of Significant Accounting Policies [Line Items]
Award vesting period (in years)			2 years
Stock Options and Restricted Stock | Maximum
Summary of Significant Accounting Policies [Line Items]
Award vesting period (in years)			5 years