Segment Reporting - Reconciliation (Details) - USD ($) $ in Thousands		3 Months Ended			9 Months Ended
		Sep. 30, 2017	Sep. 30, 2016		Sep. 30, 2017		Sep. 30, 2016
Segment Reporting Information [Line Items]
Income before income tax expense		$ 15,393	$ 7,930	[1]	$ 34,010	[2]	$ 48,388	[1]
Interest and other income		(168)	(240)	[1]	(102)	[2]	(340)	[1]
Interest expense		2,863	1,270	[1]	8,760	[2]	2,855	[1]
Operating Income		18,088	8,960	[1]	42,668	[2]	50,903	[1]
Depreciation and amortization		11,509	8,295	[1]	30,435	[2]	23,337	[1]
General and administrative	[3]	25,566	18,009	[1]	69,405	[2]	55,188	[1]
Less
Net asset optimization expenses	[4]	(320)	108	[1]	(681)	[2]	(42)	[1]
Net, (loss) gain on non-trading derivative instruments		(2,752)	(609)		(34,225)		2,887
Net, Cash settlements on non-trading derivative instruments					20,816	[5]	18,693	[6]
Retail Gross Margin		50,570	45,228		158,319		123,610
Non-trading
Less
Net, (loss) gain on non-trading derivative instruments		(2,568)	(1,183)		(34,146)		2,519
Net, Cash settlements on non-trading derivative instruments		$ 7,481	$ (8,889)		$ 19,016		$ 3,341

[1] Financial information has been recast to include results attributable to the acquisition of the Major Energy Companies by an affiliate on April 15, 2016. See Note 2 and 3 "Basis of Presentation and Summary of Significant Accounting Policies" and "Acquisitions," respectively, for further discussion.

[2] Financial information has been recast to include results attributable to the acquisition of Perigee Energy, LLC by an affiliate on February 3, 2017. See Notes 2 and 3 "Basis of Presentation and Summary of Significant Accounting Policies" and "Acquisitions," respectively, for further discussion.

[3] General and administrative expense includes general and administrative expense—affiliates of $5,500 and $3,078 for the three months ended September 30, 2017 and 2016, respectively, and $18,800 and $11,521 for the nine months ended September 30, 2017 and 2016, respectively.

[4] Net asset optimization revenues (expenses) includes asset optimization revenues—affiliates of $0 and $0 for the three months ended September 30, 2017 and 2016, respectively, and asset optimization revenues—affiliates cost of revenues of $0 and $0 for the three months ended September 30, 2017 and 2016, respectively, and asset optimization revenues—affiliates of $0 and $154 for the nine months ended September 30, 2017 and 2016, respectively, and asset optimization revenue—affiliates cost of revenues of $0 and $1,633 for the nine months ended September 30, 2017 and 2016, respectively.

[5] Financial information has been recast to include results attributable to the acquisition of Perigee Energy, LLC by an affiliate on February 3, 2017. See Notes 2 and 3 "Basis of Presentation and Summary of Significant Accounting Policies" and "Acquisitions," respectively, for further discussion.

[6] Financial information has been recast to include results attributable to the acquisition of the Major Energy Companies by an affiliate on April 15, 2016. See Notes 2 and 3 "Basis of Presentation and Summary of Significant Accounting Policies" and "Acquisitions," respectively, for further discussion.