Segment Data (Details) - USD ($) $ in Thousands		3 Months Ended
		Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2019
Segment Reporting Information [Line Items]
Affiliates (1)	[1]	$ 106,699	$ 62,965
Third party		56,702	89,518
Net revenues		163,401	152,483
Cost of materials and other		101,293	96,265
Operating expenses (excluding depreciation and amortization presented below)		14,744	16,058
Segment contribution margin		47,364	40,160
General and administrative expenses		6,130	4,473
Depreciation and amortization		6,299	6,574
(Gain) loss on asset disposals		(107)	2
Other Operating Income (Expense), Net		107	(2)
Operating income		35,042	29,111
Capital spending		3,028	904
Total assets		946,236		$ 744,447
Pipelines and transportation
Segment Reporting Information [Line Items]
Affiliates (1)		38,502	36,659
Third party		9,465	3,974
Net revenues		47,967	40,633
Operating expenses (excluding depreciation and amortization presented below)		11,456	10,834
Segment contribution margin		30,413	24,232
Capital spending		445	424
Total assets		849,840		537,580
Wholesale marketing and terminalling
Segment Reporting Information [Line Items]
Affiliates (1)		68,197	26,306
Third party		47,237	85,544
Net revenues		115,434	111,850
Operating expenses (excluding depreciation and amortization presented below)		3,288	5,224
Segment contribution margin		16,951	15,928
Capital spending		2,583	480
Total assets		96,396		$ 206,867
Service
Segment Reporting Information [Line Items]
Cost of materials and other		101,293	96,265
Service | Pipelines and transportation
Segment Reporting Information [Line Items]
Cost of materials and other		6,098	5,567
Service | Wholesale marketing and terminalling
Segment Reporting Information [Line Items]
Cost of materials and other		$ 95,195	$ 90,698

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