Segment Reporting - Information Concerning Business Activities (Details) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021 USD ($)	Jun. 30, 2020 USD ($)	Jun. 30, 2021 USD ($) segment	Jun. 30, 2020 USD ($)
Segment Reporting [Abstract]
Number of reportable segments | segment			3
Number of operating segments | segment			3
Segment Reporting Information [Line Items]
Revenues	$ 486,744	$ 152,286	$ 812,235	$ 505,763
Segment operating earnings (losses)	6,335	2,935	10,186	(17,005)
Depreciation and amortization	4,801	4,278	9,854	8,751
Property and equipment additions	3,432	668	3,602	2,880
Leasehold Improvements
Segment Reporting Information [Line Items]
Property and equipment additions		300	8	500
Crude Oil Marketing
Segment Reporting Information [Line Items]
Revenues	463,092	140,141	767,115	477,362
Depreciation and amortization	1,641	1,857	3,439	3,864
Property and equipment additions	492	18	702	2,050
Inventory liquidation (gains) losses	(3,700)	(6,000)	(10,600)	18,200
Transportation
Segment Reporting Information [Line Items]
Revenues	23,497	12,145	44,732	28,401
Depreciation and amortization	2,937	2,421	5,938	4,887
Property and equipment additions	2,761	323	2,703	364
Pipeline and storage
Segment Reporting Information [Line Items]
Revenues	155	0	388	0
Depreciation and amortization	223	0	477	0
Property and equipment additions	179	0	189	0
Operating segments
Segment Reporting Information [Line Items]
Revenues	487,278	152,286	812,988	505,763
Segment operating earnings (losses)	9,296	5,666	16,523	(11,380)
Operating segments | Crude Oil Marketing
Segment Reporting Information [Line Items]
Revenues	463,092	140,141	767,115	477,362
Segment operating earnings (losses)	8,370	6,830	15,388	(10,821)
Operating segments | Transportation
Segment Reporting Information [Line Items]
Revenues	23,535	12,145	44,803	28,401
Segment operating earnings (losses)	1,482	(1,164)	2,256	(559)
Operating segments | Pipeline and storage
Segment Reporting Information [Line Items]
Revenues	651	0	1,070	0
Segment operating earnings (losses)	(556)	0	(1,121)	0
Intersegment
Segment Reporting Information [Line Items]
Revenues	(534)	0	(753)	0
Intersegment | Crude Oil Marketing
Segment Reporting Information [Line Items]
Revenues	0	0	0	0
Intersegment | Transportation
Segment Reporting Information [Line Items]
Revenues	(38)	0	(71)	0
Intersegment | Pipeline and storage
Segment Reporting Information [Line Items]
Revenues	(496)	0	(682)	0
Other
Segment Reporting Information [Line Items]
Revenues	0	0	0	0
Segment operating earnings (losses)	0	0	0	0
Depreciation and amortization	0	0	0	0
Property and equipment additions	$ 0	$ 327	$ 8	$ 466