Fair value as of the balance sheet date of derivative instrument not designated as hedging instrument and classified as an asset.

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Amount of transfer of financial instrument classified as an asset into level 3 of the fair value hierarchy.

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Fair value as of the balance sheet date of all derivative assets not designated as hedging instruments.

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Fair value as of the balance sheet date of all derivatives not designated as hedging instruments.

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Amount, after valuation allowance, of financing receivable held for sale and not part of disposal group. Excludes loan covered under loss sharing agreement and loan classified as investment in debt security.

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Fair value of all derivative liabilities not designated as a hedging instrument.

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No definition available.

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Amount of investments classified as other.

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Aggregate amount of servicing assets that are subsequently measured at fair value and servicing assets that are subsequently measured using the amortization method.

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Fair value of an asset representing net future revenue from contractually specified servicing fees, late charges, and other ancillary revenues, in excess of future costs related to servicing arrangements.

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Fair Value Measurements - Assets and Liabilities Measured on Recurring Basis (Details) - USD ($)	12 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2020
Estimate fair value [Member] \| Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Mortgage loans held for sale	$ 2,370,200,000	$ 2,021,100,000
Mortgage servicing rights	10,600,000	4,100,000
Estimate fair value [Member] \| Recurring [Member] \| Interest rate lock commitments [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivatives not designated as hedging instruments	(135,800,000)	17,200,000
Mortgage hedging instruments and commitments	(183,500,000)	(700,000)
Estimate fair value [Member] \| Recurring [Member] \| Forward Sales Of MBS [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivatives not designated as hedging instruments	317,800,000	8,500,000
Mortgage loans held for sale	2,386,000,000	2,027,300,000
Mortgage servicing rights	10,600,000	4,100,000
Mortgage hedging instruments and commitments	(12,400,000)	(1,000,000.0)
Mortgage hedging instruments and commitments	330,200,000	8,700,000
Loans Receivable [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Net transfers to (out of) Level 3	7,000,000.0	(400,000)
Interest rate lock commitments [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Interest rate lock commitments	47,700,000	17,900,000
Recurring [Member] \| Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Mortgage loans held for sale	0	0
Mortgage servicing rights	0	0
Recurring [Member] \| Level 1 [Member] \| Interest rate lock commitments [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivatives not designated as hedging instruments	0	0
Recurring [Member] \| Level 1 [Member] \| Forward Sales Of MBS [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivatives not designated as hedging instruments	0	0
Recurring [Member] \| Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Mortgage loans held for sale	2,356,100,000	2,009,400,000
Mortgage servicing rights	0	0
Recurring [Member] \| Level 2 [Member] \| Interest rate lock commitments [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivatives not designated as hedging instruments	(135,800,000)	17,200,000
Recurring [Member] \| Level 2 [Member] \| Forward Sales Of MBS [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivatives not designated as hedging instruments	317,800,000	8,500,000
Recurring [Member] \| Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt securities collateralized by residential real estate		0	$ 3,900,000
Mortgage loans held for sale	14,100,000	11,700,000	15,100,000
Mortgage servicing rights	10,600,000	4,100,000	$ 17,100,000
Recurring [Member] \| Level 3 [Member] \| Measurement Input, Prepayment Rate [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Servicing Asset at Fair Value, Amount	0.12
Recurring [Member] \| Level 3 [Member] \| Measurement Input, Discount Rate [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Servicing Asset at Fair Value, Amount	0.11
Recurring [Member] \| Level 3 [Member] \| Measurement Input, Default Rate [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Servicing Asset at Fair Value, Amount	0.08
Recurring [Member] \| Level 3 [Member] \| Interest rate lock commitments [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivatives not designated as hedging instruments	0	0
Recurring [Member] \| Level 3 [Member] \| Forward Sales Of MBS [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivatives not designated as hedging instruments	$ 0	$ 0