Securities and Commodity Financing Transactions (Details) - USD ($) $ in Millions	Sep. 30, 2020	Sep. 30, 2019
Securities Financing Transaction [Line Items]
Securities sold under agreements to repurchase	$ 3,155.5	$ 2,773.7
Securities loaned	1,441.9	1,459.9
Gross amount of secured financing	4,597.4	4,233.6
Securities purchased under agreements to resell, gross	1,696.2	1,474.4
Securities borrowed, gross	1,440.0	1,423.2
Securities sold under agreements to repurchase, gross	3,155.5	2,823.6
Securities loaned, gross	1,441.9	1,459.9
Securities Purchased under Agreements to Resell, Offset	0.0	(49.9)
Securities borrowed, Offset	0.0	0.0
Securities sold under agreements to repurchase, Offset	0.0	(49.9)
Securities loaned, Offset	0.0	0.0
Securities purchased under agreements to resell	1,696.2	1,424.5
Securities borrowed	1,440.0	1,423.2
U.S. Treasury Obligations [Member]
Securities Financing Transaction [Line Items]
Securities sold under agreements to repurchase	815.8	108.8
U.S. Government Agency Obligations [Member]
Securities Financing Transaction [Line Items]
Securities sold under agreements to repurchase	279.5	359.5
Asset-backed Obligations [Member]
Securities Financing Transaction [Line Items]
Securities sold under agreements to repurchase	18.0	96.7
Agency Mortgage-backed Obligations [Member]
Securities Financing Transaction [Line Items]
Securities sold under agreements to repurchase	1,990.0	2,208.7
Corporate Bonds [Member]
Securities Financing Transaction [Line Items]
Securities sold under agreements to repurchase	52.2	0.0
Equity Securities [Member]
Securities Financing Transaction [Line Items]
Securities loaned	1,441.9	1,459.9
Overnight and Open [Member]
Securities Financing Transaction [Line Items]
Securities sold under agreements to repurchase	1,736.3	1,553.9
Securities loaned	1,441.9	1,459.9
Gross amount of secured financing	3,178.2	3,013.8
Less than 30 Days [Member]
Securities Financing Transaction [Line Items]
Securities sold under agreements to repurchase	1,069.2	565.8
Securities loaned	0.0	0.0
Gross amount of secured financing	1,069.2	565.8
30-90 Days [Member]
Securities Financing Transaction [Line Items]
Securities sold under agreements to repurchase	325.0	654.0
Securities loaned	0.0	0.0
Gross amount of secured financing	325.0	654.0
Over 90 Days [Member]
Securities Financing Transaction [Line Items]
Securities sold under agreements to repurchase	25.0	0.0
Securities loaned	0.0	0.0
Gross amount of secured financing	$ 25.0	$ 0.0

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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