Mortgage Loans - Mortgage Loans Held for Sale Textual (Details) - USD ($) $ in Millions	12 Months Ended
Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2017
Loans Receivable [Line Items]
Mortgage loans held for sale, principal amount	$ 1,000.0	$ 776.1
Loans Receivable Held-for-sale, Net, Not Part of Disposal Group	1,072.0	796.4
Payments for Origination of Mortgage Loans Held-for-sale	8,700.0	7,600.0	$ 6,800.0
Proceeds from Sale of Mortgage Loans Held-for-sale	8,400.0	7,400.0	6,800.0
Net gain on sales of loans	$ 319.4	265.1	$ 251.1
Percentage of Mortgage Loans Sold to Major Purchasers	93.00%
Percentage Of Mortgage Loans Sold To Major Purchaser	32.00%
Uncommitted Loans [Member]
Loans Receivable [Line Items]
Loans Receivable Held-for-sale, Net, Not Part of Disposal Group	$ 663.8	575.9
Uncommitted Loans [Member] \| Hedging Instruments Related To IRLCs [Member]
Loans Receivable [Line Items]
Derivative Asset, Notional Amount	$ 663.8	$ 575.8

The percentage of mortgage loans sold to major purchasers during the period.

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+ References

No definition available.

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For an entity that discloses a concentration risk in relation to quantitative amount, which serves as the "benchmark" (or denominator) in the equation, this concept represents the concentration percentage derived from the division.

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Nominal or face amount used to calculate payments on the derivative asset.

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The net gain (loss) resulting from a sale of loans, including adjustments to record loans classified as held-for-sale at the lower-of-cost-or-market and fair value adjustments to loan held for investment purposes.

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Amount, after allowance for bad debt, of loan receivables held-for-sale that are not part of a disposal group. Excludes loans and leases covered under loss sharing agreements and loans classified as debt securities.

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The amount of cash paid for the origination of mortgages that are held for sale.

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- Definition

This is the principal amount outstanding for loans which are in the process of being securitized as of the date of the statement of financial position (across all types of loans).

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The cash inflow from sales of loans that are secured with real estate mortgages and are held with the intention to resell in the near future.

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