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Physical Commodities Inventory - Physical Commodities Inventory by CIP and Finished (Details) - USD ($) $ in Millions | Dec. 31, 2018 | Sep. 30, 2018
--- | --- | ---
Inventory [Line Items] |  |
Physical Ag & Energy(1) | $ 151.1 | $ 114.7
Precious metals - held by non-broker-dealer subsidiaries(3) | 164.4 | 156.9
Physical commodities inventory | 222.5 | 222.5
Physical commodities inventory - precious metals [Member] |  |
Inventory [Line Items] |  |
Precious metals - held by non-broker-dealer subsidiaries(3) | 13.3 | 42.1
Finished commodities | $ 58.1 | $ 65.7

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