Fair Value Measurements - Assets Measured on a Nonrecurring Basis (Details) $ in Millions	Sep. 30, 2023 USD ($)	Sep. 30, 2022 USD ($)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Mortgage loans held for sale	$ 2,519.9	$ 2,386.0
Inventories [Member] \| Measurement Input, Discount Rate [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other Real Estate Owned, Measurement Input	0.12
Nonrecurring [Member] \| Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Mortgage loans held for sale	$ 0.0	0.0
Other mortgage loans	0.0	0.0
Nonrecurring [Member] \| Level 2 [Member] \| Inventories [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Inventories	0.0	0.0
Nonrecurring [Member] \| Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Mortgage loans held for sale	30.7	15.8
Other mortgage loans	2.2	1.5
Nonrecurring [Member] \| Level 3 [Member] \| Inventories [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Inventories	$ 28.8	$ 0.0

Fair value portion of probable future economic benefits obtained or controlled by an entity as a result of past transactions or events.

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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Fair value portion of loan receivable, including, but not limited to, mortgage loans held for investment, finance receivables held for investment, policy loans on insurance contracts.

+ References

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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.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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Value of input used to measure real estate owned by financial institution by financial institution which is not directly related to its business.

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