Receivables From Customers, Net and Notes Receivable, Net (Notes)	6 Months Ended
Mar. 31, 2020
Receivables from customers and notes receivable, net [Abstract]
Financing Receivables [Text Block]	Allowance for Doubtful Accounts The allowance for doubtful accounts related to deposits with and receivables from broker-dealers, clearing organizations, and counterparties was $1.3 million and $36.9 million as of March 31, 2020 and September 30, 2019, respectively. During the three months ended March 31, 2020, the Company charged off $35.6 million of receivables against the allowance for doubtful accounts related to the physical coal business, which the Company exited in fiscal 2018. The allowance for doubtful accounts related to receivables from clients was $17.2 million and $11.7 million as of March 31, 2020 and September 30, 2019, respectively. The allowance increase is related to additional bad debt reserves as discussed below and recoverable amounts due from affiliated party and recorded in ‘other assets’ in the condensed consolidated balance sheets. The Company had no allowance for doubtful accounts related to notes receivable as of March 31, 2020 and September 30, 2019. During the three months ended March 31, 2020, the Company recorded bad debt expense of $4.4 million, primarily related to $3.9 million of OTC client account deficits in the Commercial Hedging segment, $0.3 million of client deficits in the Clearing & Execution Services segment and $0.2 million in uncollected receivables in the Physical Commodities segment. During the three months ended March 31, 2019, the Company recorded bad debt expense of $0.7 million, primarily related to client account deficits in the Commercial Hedging segment. During the six months ended March 31, 2020, the Company recorded bad debt expense of $4.4 million, as discussed above. During the six months ended March 31, 2019, the Company recorded bad debt expense of $1.0 million, primarily related to client account deficits in the Commercial Hedging and Clearing & Execution Services segments. Additionally, during the six months ended March 31, 2019, the Company reached settlements with clients, paying $8.4 million related to demurrage, dead freight, and other penalty charges regarding coal supplied during fiscal 2017. The settlement amounts paid were less than the accrued liability for the transactions recorded during fiscal 2017 and fiscal 2018, and accordingly the Company recorded a recovery on the bad debt on physical coal of $2.4 million.

Allowance for Doubtful Accounts

The allowance for doubtful accounts related to deposits with and receivables from broker-dealers, clearing organizations, and counterparties was $1.3 million and $36.9 million as of March 31, 2020 and September 30, 2019, respectively. During the three months ended March 31, 2020, the Company charged off $35.6 million of receivables against the allowance for doubtful accounts related to the physical coal business, which the Company exited in fiscal 2018.

The allowance for doubtful accounts related to receivables from clients was $17.2 million and $11.7 million as of March 31, 2020 and September 30, 2019, respectively. The allowance increase is related to additional bad debt reserves as discussed below and recoverable amounts due from affiliated party and recorded in ‘other assets’ in the condensed consolidated balance sheets. The Company had no allowance for doubtful accounts related to notes receivable as of March 31, 2020 and September 30, 2019.

During the three months ended March 31, 2020, the Company recorded bad debt expense of $4.4 million, primarily related to $3.9 million of OTC client account deficits in the Commercial Hedging segment, $0.3 million of client deficits in the Clearing & Execution Services segment and $0.2 million in uncollected receivables in the Physical Commodities segment. During the three months ended March 31, 2019, the Company recorded bad debt expense of $0.7 million, primarily related to client account deficits in the Commercial Hedging segment.

During the six months ended March 31, 2020, the Company recorded bad debt expense of $4.4 million, as discussed above. During the six months ended March 31, 2019, the Company recorded bad debt expense of $1.0 million, primarily related to client account deficits in the Commercial Hedging and Clearing & Execution Services segments.

Additionally, during the six months ended March 31, 2019, the Company reached settlements with clients, paying $8.4 million related to demurrage, dead freight, and other penalty charges regarding coal supplied during fiscal 2017. The settlement amounts paid were less than the accrued liability for the transactions recorded during fiscal 2017 and fiscal 2018, and accordingly the Company recorded a recovery on the bad debt on physical coal of $2.4 million.