Commodity and Other Repurchase Agreements (Details) - USD ($) $ in Millions	Sep. 30, 2018	Sep. 30, 2017
Securities sold under agreements to repurchase	$ 1,936.7	$ 1,393.1
Fair Value of Securities Received as Collateral that Can be Resold or Repledged	1,294.8	631.7
Fair Value of Securities Received as Collateral that Have Been Resold or Repledged	473.9	306.9
Financial Instruments Owned and Pledged as Collateral, Amount Eligible to be Repledged by Counterparty	123.0	19.4
Securities Loaned, Fair Value of Collateral	267.9	108.4
Financial Instruments Owned and Pledged as Collateral, Amount Not Eligible to be Repledged by Counterparty	1,481.1	1,306.4
Securities Loaned	277.9	111.1
Collateralized Financings	2,214.6	1,504.2
Sales Repurchase Agreements	1.9	0.8
Securities Sold under Agreements to Repurchase, Fair Value of Collateral	123.0	19.4
Trading Securities Pledged as Collateral	27.1	12.7
Pledged Financial Instruments, Not Separately Reported, Securities for Repurchase Agreements	369.8	100.2
Maturity Overnight [Member]
Securities sold under agreements to repurchase	934.9	640.2
Securities Loaned	277.9	111.1
Collateralized Financings	1,212.8	751.3
Maturity Less than 30 Days [Member]
Securities sold under agreements to repurchase	661.3	432.9
Securities Loaned	0.0	0.0
Collateralized Financings	661.3	432.9
Maturity 30 to 90 Days [Member]
Securities sold under agreements to repurchase	340.5	320.0
Securities Loaned	0.0	0.0
Collateralized Financings	340.5	320.0
Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Securities sold under agreements to repurchase		1,017.1
Asset-backed Securities [Member]
Securities sold under agreements to repurchase	50.0	36.4
US Government Debt Securities [Member]
Securities sold under agreements to repurchase	39.6	7.0
US Government Agencies Debt Securities [Member]
Securities sold under agreements to repurchase	461.7	332.6
Equity Securities [Member]
Securities Loaned	$ 277.9	$ 111.1

Financing Receivables, net - Sales/Repurchase Agreements

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The value of the collateral (typically cash) that the entity receives in a financing transaction in exchange for securities lent. This item represents a liability in the financial statements of the lender of the securities.

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Fair value of collateral permitted, by contact or custom, to be sold or re-pledged.

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Fair value of the collateral, or portion thereof, that has been re-pledged, delivered, or otherwise used.

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Fair value of financial instrument held by the entity for its own account (proprietary securities) for trading or investment purposes that are carried at fair value and pledged to counterparties as collateral for financing transactions where counterparty has the right to re-pledge such.

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The carrying amount as of the date of the latest financial statement presented of securities which are owned but transferred to serve as collateral for repurchase agreements, and for which the transferee does not have the right by contract or custom to sell or re-pledge them to an unrelated party.

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Amount, after the effects of master netting arrangements, of securities loaned to entities in exchange for collateral. Includes liabilities not subject to a master netting arrangement and not elected to be offset.

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Fair value of the securities pledged as collateral against securities loaned.

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Amount, after the effects of master netting arrangements, of funds outstanding borrowed in the form of a security repurchase agreement between the entity and another party for the sale and repurchase of identical or substantially the same securities at a date certain for a specified price. Includes liabilities not subject to a master netting arrangement and not elected to be offset.

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Fair value of securities pledged as collateral against securities sold under agreement to repurchase.

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The fair value of trading securities that serve as collateral for borrowings.

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