Note 14 - Operating Segments - Financial Data for Each Segment (Details) - USD ($) $ in Thousands		3 Months Ended		9 Months Ended
		Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2018
Revenue from contract with customer		$ 74,885	$ 115,902	$ 233,359	$ 208,836
Total revenue for reportable segment		91,756	133,158	279,564	261,311
Operating margin, excluding depreciation and amortization		21,165	18,229	56,494	54,613
Total assets (end of period)		313,975		313,975		$ 323,304
Depreciation and amortization		6,240	7,166	19,211	21,945
General and administrative expense		3,840	4,322	10,495	13,029
Asset impairment expense		83	15	2,316	631
Gain (loss) on sale of assets		(40)	(63)	1,765	300
Other income				268
Gain on sale of unconsolidated affiliate					2,225
Interest expense		3,989	4,090	12,394	12,683
Income before income taxes		6,973	2,573	14,111	8,850
Intersegment Eliminations [Member]
Total revenue for reportable segment		(1,642)	(1,644)	(4,971)	(3,243)
Operating Segments [Member]
Total revenue for reportable segment		93,398	134,802	284,535	264,554
Operating margin, excluding depreciation and amortization	[1]	21,165	18,229	56,494	54,613
Third Party [Member]
Lease revenue		11,444	11,368	31,026	31,409
Cost of product sales		18,972	50,815	64,069	73,493
Related Party [Member]
Lease revenue		5,427	5,406	15,179	20,584
Cost of product sales		32,691	44,106	99,886	67,853
Asphalt Terminalling Services [Member]
Revenue from contract with customer		11,277	12,132	33,208	36,205
Total revenue for reportable segment		28,148	29,308	79,413	88,033
Operating expense, excluding depreciation and amortization		11,025	11,683	34,980	38,412
Operating margin, excluding depreciation and amortization		17,123	17,625	44,433	49,621
Total assets (end of period)		145,761	143,454	145,761	143,454
Asphalt Terminalling Services [Member] | Third Party [Member]
Lease revenue		11,444	11,288	31,026	30,762
Asphalt Terminalling Services [Member] | Related Party [Member]
Lease revenue		5,427	5,406	15,179	20,584
Crude Oil Pipeline Services [Member]
Revenue from contract with customer		56,561	99,113	179,792	151,420
Total revenue for reportable segment		56,561	99,153	179,792	151,872
Operating expense, excluding depreciation and amortization		2,638	3,094	8,109	8,420
Operating margin, excluding depreciation and amortization		618	(506)	2,757	(1,137)
Total assets (end of period)		96,221	171,841	96,221	171,841
Crude Oil Pipeline Services [Member] | Intersegment Eliminations [Member]
Intersegment operating expense		1,642	1,644	4,971	3,243
Crude Oil Pipeline Services [Member] | Third Party [Member]
Lease revenue			40		452
Cost of product sales		18,972	50,815	64,069	73,493
Crude Oil Pipeline Services [Member] | Related Party [Member]
Cost of product sales		32,691	44,106	99,886	67,853
Crude Oil Terminalling Services [Member]
Revenue from contract with customer		4,225	1,923	11,819	9,418
Total revenue for reportable segment		4,503	2,154	12,672	9,845
Operating expense, excluding depreciation and amortization		1,212	928	3,511	3,115
Operating margin, excluding depreciation and amortization		3,291	1,226	9,161	6,730
Total assets (end of period)		66,045	67,213	66,045	67,213
Crude Oil Terminalling Services [Member] | Third Party [Member]
Lease revenue			9		35
Crude Oil Trucking Services [Member]
Revenue from contract with customer		2,822	2,734	8,540	11,793
Total revenue for reportable segment		4,186	4,187	12,658	14,804
Operating expense, excluding depreciation and amortization		4,053	4,303	12,515	15,405
Operating margin, excluding depreciation and amortization		133	(116)	143	(601)
Total assets (end of period)		5,948	3,731	5,948	3,731
Crude Oil Trucking Services [Member] | Third Party [Member]
Lease revenue			31		160
Service [Member] | Third Party [Member]
Revenue from contract with customer		15,716	12,743	47,329	44,164
Service [Member] | Related Party [Member]
Revenue from contract with customer		3,956	5,396	12,257	17,780
Service [Member] | Asphalt Terminalling Services [Member] | Third Party [Member]
Revenue from contract with customer		7,385	6,921	21,217	18,693
Service [Member] | Asphalt Terminalling Services [Member] | Related Party [Member]
Revenue from contract with customer		3,892	5,211	11,991	17,512
Service [Member] | Crude Oil Pipeline Services [Member] | Third Party [Member]
Revenue from contract with customer		1,284	1,165	5,753	4,270
Service [Member] | Crude Oil Pipeline Services [Member] | Related Party [Member]
Revenue from contract with customer		64	185	266	268
Service [Member] | Crude Oil Terminalling Services [Member] | Intersegment Eliminations [Member]
Revenue from contract with customer		278	222	853	392
Service [Member] | Crude Oil Terminalling Services [Member] | Third Party [Member]
Revenue from contract with customer		4,225	1,923	11,819	9,418
Service [Member] | Crude Oil Trucking Services [Member] | Intersegment Eliminations [Member]
Revenue from contract with customer		1,364	1,422	4,118	2,851
Service [Member] | Crude Oil Trucking Services [Member] | Third Party [Member]
Revenue from contract with customer		2,822	2,734	8,540	11,783
Product [Member] | Third Party [Member]
Revenue from contract with customer		55,213	97,763	173,773	146,892
Product [Member] | Related Party [Member]
Revenue from contract with customer			482		482
Product [Member] | Asphalt Terminalling Services [Member] | Related Party [Member]
Revenue from contract with customer			482		482
Product [Member] | Crude Oil Pipeline Services [Member] | Third Party [Member]
Revenue from contract with customer		55,213	97,763	173,773	146,882
Product [Member] | Crude Oil Trucking Services [Member] | Third Party [Member]
Revenue from contract with customer					$ 10

[1] The following table reconciles segment operating margin (excluding depreciation and amortization) to income before income taxes (in thousands):