Segment Reporting - Information Concerning Business Activities (Details) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019 USD ($)	Jun. 30, 2018 USD ($)	Jun. 30, 2019 USD ($) segment	Jun. 30, 2018 USD ($)
Segment Reporting [Abstract]
Number of reportable segments | segment			2
Number of operating segments | segment			2
Segment Reporting Information [Line Items]
Revenues	$ 484,433	$ 452,417	$ 929,601	$ 839,673
Segment operating earnings	(643)	4,298	4,610	5,375
Depreciation and amortization	4,284	2,262	7,873	4,674
Inventory liquidation (losses) gains	1,000
Tractors and Tank Storage and Throughput Arrangements
Segment Reporting Information [Line Items]
Property and equipment additions	3,600		4,100
Marketing
Segment Reporting Information [Line Items]
Revenues	467,040	438,791	896,801	812,429
Inventory liquidation (losses) gains		(1,900)	(3,500)	(2,500)
Transportation
Segment Reporting Information [Line Items]
Revenues	17,393	13,626	32,800	27,244
Reporting Segments
Segment Reporting Information [Line Items]
Revenues	484,433	452,417	929,601	839,673
Segment operating earnings	1,939	6,582	9,876	9,942
Depreciation and amortization	4,284	2,262	7,873	4,674
Property and equipment additions	4,770	1,849	13,121	2,715
Reporting Segments | Marketing
Segment Reporting Information [Line Items]
Revenues	467,040	438,791	896,801	812,429
Segment operating earnings	962	5,772	8,060	8,730
Depreciation and amortization	2,304	1,336	4,426	2,833
Property and equipment additions	1,348	277	3,002	1,070
Reporting Segments | Transportation
Segment Reporting Information [Line Items]
Revenues	17,393	13,626	32,800	27,244
Segment operating earnings	977	810	1,816	1,212
Depreciation and amortization	1,980	926	3,447	1,841
Property and equipment additions	3,422	1,572	10,119	1,645
Reporting Segments | Oil and Gas
Segment Reporting Information [Line Items]
Revenues	0	0	0	0
Segment operating earnings	0	0	0	0
Depreciation and amortization	0	0	0	0
Property and equipment additions	$ 0	$ 0	$ 0	$ 0