Segment Data (Details) - USD ($) $ in Thousands		3 Months Ended		6 Months Ended
		Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2019
Segment Reporting Information [Line Items]
Affiliates (1)	[1]	$ 87,629	$ 61,918	$ 194,328	$ 124,883
Third party		30,008	93,424	86,710	182,942
Net revenues		117,637	155,342	281,038	307,825
Cost of materials and other		43,892	93,854	145,185	190,119
Operating expenses (excluding depreciation and amortization presented below)		12,449	17,327	27,193	33,385
Segment contribution margin		61,296	44,161	108,660	84,321
General and administrative expenses		4,721	5,293	10,851	9,766
Depreciation and amortization		8,694	6,639	14,993	13,213
Gain on asset disposals		0	(27)	(107)	(25)
Other Operating Income (Expense), Net		0	27	107	25
Operating income		47,881	32,256	82,923	61,367
Capital spending		652	1,342	3,681	2,246
Total assets		973,737		973,737		$ 744,447
Pipelines and transportation
Segment Reporting Information [Line Items]
Affiliates (1)		61,394	36,731	99,897	73,390
Third party		2,032	7,477	11,496	11,451
Net revenues		63,426	44,208	111,393	84,841
Operating expenses (excluding depreciation and amortization presented below)		9,731	12,728	21,187	23,562
Segment contribution margin		42,513	24,123	72,926	48,355
Capital spending		417	818	863	1,242
Total assets		836,510		836,510		537,580
Wholesale marketing and terminalling
Segment Reporting Information [Line Items]
Affiliates (1)		26,235	25,187	94,431	51,493
Third party		27,976	85,947	75,214	171,491
Net revenues		54,211	111,134	169,645	222,984
Operating expenses (excluding depreciation and amortization presented below)		2,718	4,599	6,006	9,823
Segment contribution margin		18,783	20,038	35,734	35,966
Capital spending		235	524	2,818	1,004
Total assets		137,227		137,227		$ 206,867
Service
Segment Reporting Information [Line Items]
Cost of materials and other		43,892	93,854	145,185	190,119
Service | Pipelines and transportation
Segment Reporting Information [Line Items]
Cost of materials and other		11,182	7,357	17,280	12,924
Service | Wholesale marketing and terminalling
Segment Reporting Information [Line Items]
Cost of materials and other		$ 32,710	$ 86,497	$ 127,905	$ 177,195

[1] See Note 3 for a description of our material affiliate revenue transactions.