Summary of Significant Accounting Policies - Schedule of Spot Trades (Details) - Spot Trade - USD ($) $ in Millions	Jun. 30, 2019	Dec. 31, 2018
Accounts Receivable
Assets:
Gross Assets	$ 465.3	$ 815.7
Offset on the Balance Sheet	(421.2)	(745.2)
Net Assets	44.1	70.5
Accounts Payable
Liabilities:
Gross Liabilities	452.0	760.8
Offset on the Balance Sheet	(421.2)	(745.2)
Net Liabilities	$ 30.8	$ 15.6

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