Segment Reporting - Reconciliation of Retail Gross Margin to Income Before Income Tax Expense (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Segment Reporting Information [Line Items]
(Loss) income before income tax (benefit) expense	$ (29,095)	$ 11,993
Interest and other income	(86)	(160)
Interest expense	1,311	1,553
Operating (loss) income	(27,870)	13,386
Depreciation and amortization	6,036	8,796
General and administrative	12,671	25,676
Less:
Net asset optimization (expense) revenues	(140)	321
Net, gain (loss) on non-trading derivative instruments	7,024	(24,587)
Net, Cash settlements on non-trading derivative instruments	(1,185)	16,293
Non-recurring event - Winter Storm Uri	(64,900)	0
Retail Gross Margin	50,012	55,461
Non-trading
Less:
Net, gain (loss) on non-trading derivative instruments	7,054	(24,533)
Net, Cash settlements on non-trading derivative instruments	$ (1,189)	$ 16,609