Physical Commodities Inventory - Physical Commodities Inventory (Details) - USD ($) $ in Millions	Sep. 30, 2022	Sep. 30, 2021
Inventory [Line Items]
Physical Ag & Energy	$ 223.6	$ 248.6
Precious metals - held by broker-dealer subsidiary	359.8	359.9
Physical commodities inventory	513.5	447.5
Physical Commodities Inventory - Precious Metals
Inventory [Line Items]
Precious metals - held by broker-dealer subsidiary	136.3	111.2
Precious metals - held by non-broker-dealer subsidiaries	$ 153.6	$ 87.7

Physical commodities inventory at fair value - precious metals

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Carrying amount, net of valuation reserves and adjustments, as of the balance sheet date of merchandise or goods held by the company that are readily available for sale.

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