Segment Reporting, Information Concerning Business Activities (Details) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017 USD ($)	Sep. 30, 2016 USD ($)	Sep. 30, 2017 USD ($) segment	Sep. 30, 2016 USD ($)
Segment Reporting [Abstract]
Number of reportable segments | segment			3
Revenues	$ 295,311	$ 256,877	$ 913,600	$ 800,571
Segment operating (losses) earnings	(1,290)	(1,822)	(2,255)	6,118
Depreciation, depletion and amortization	3,240	4,514	10,772	14,385
Reportable segments
Segment Reporting [Abstract]
Revenues	295,311	256,877	913,600	800,571
Segment operating (losses) earnings	1,497	292	4,629	12,370
Depreciation, depletion and amortization	3,240	4,514	10,772	14,385
Property and equipment additions	357	2,414	2,465	7,186
Reportable segments | Marketing
Segment Reporting [Abstract]
Revenues	282,229	243,704	872,020	758,627
Segment operating (losses) earnings	2,412	1,265	5,496	13,148
Depreciation, depletion and amortization	1,911	2,418	5,957	7,621
Property and equipment additions	178	0	451	514
Reportable segments | Transportation
Segment Reporting [Abstract]
Revenues	13,082	12,310	40,153	39,517
Segment operating (losses) earnings	(915)	(430)	(920)	444
Depreciation, depletion and amortization	1,329	1,701	4,392	5,536
Property and equipment additions	179	2,329	189	6,480
Reportable segments | Oil and Gas (1)
Segment Reporting [Abstract]
Revenues	0	863	1,427	2,427
Segment operating (losses) earnings	0	(543)	53	(1,222)
Depreciation, depletion and amortization	0	395	423	1,228
Property and equipment additions	$ 0	$ 85	$ 1,825	$ 192