Fair Value Measurements and Disclosures about Fair Value of Financial Instruments - Significant unobservable inputs (Level 3) used in the valuation of assets measured at fair value on a recurring basis (Details) - Interest rate lock commitments	Mar. 31, 2021	Sep. 30, 2020
Pull-through rate [Member] | Minimum [Member]
Fixed interest rate	57.00%	0.00%
Pull-through rate [Member] | Maximum [Member]
Fixed interest rate	100.00%	100.00%
Pull-through rate [Member] | Weighted Average [Member]
Fixed interest rate	87.00%	80.00%
Direct costs to close [Member] | Minimum [Member]
Fixed interest rate	0.34%	0.31%
Direct costs to close [Member] | Maximum [Member]
Fixed interest rate	1.55%	1.01%
Direct costs to close [Member] | Weighted Average [Member]
Fixed interest rate	0.78%	0.52%