Note 11 - Operating Segments - Financial Data for Each Segment (Details) - USD ($) $ in Thousands		3 Months Ended
		Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2019
Revenue from contract with customer		$ 64,358	$ 79,029
Lease revenue		14,752	14,703
Total revenue for reportable segment		79,110	93,732
Operating margin, excluding depreciation and amortization		17,790	17,862
Total assets (end of period)		290,072		$ 301,940
Depreciation and amortization		6,094	6,734
General and administrative expense		3,540	3,693
Asset impairment expense		5,122	1,119
Gain (loss) on sale of assets		(185)	1,724
Other income		558
Interest expense		3,399	4,271
Income before income taxes		8	3,769
Intersegment Eliminations [Member]
Total revenue for reportable segment		(1,425)	(1,627)
Operating Segments [Member]
Total revenue for reportable segment		80,535	95,359
Operating margin, excluding depreciation and amortization	[1]	17,790	17,862
Third Party [Member]
Lease revenue		9,831	9,763
Cost of product sales		14,221	24,587
Related Party [Member]
Lease revenue		4,921	4,940
Cost of product sales		28,254	30,774
Asphalt Terminalling Services [Member]
Total revenue for reportable segment		25,683	25,803
Operating expense, excluding depreciation and amortization		12,026	12,285
Operating margin, excluding depreciation and amortization		13,657	13,518
Total assets (end of period)		143,621	147,844
Asphalt Terminalling Services [Member] | Operating Segments [Member]
Revenue from contract with customer		10,931	11,100
Lease revenue		14,752	14,703
Total revenue for reportable segment		25,683	25,803
Asphalt Terminalling Services [Member] | Third Party [Member]
Lease revenue		9,831	9,763
Asphalt Terminalling Services [Member] | Related Party [Member]
Lease revenue		4,921	4,940
Crude Oil Pipeline Services [Member]
Total revenue for reportable segment		47,554	61,523
Operating expense, excluding depreciation and amortization		2,123	2,722
Operating margin, excluding depreciation and amortization		1,531	1,813
Total assets (end of period)		79,180	98,722
Crude Oil Pipeline Services [Member] | Intersegment Eliminations [Member]
Intersegment operating expense		1,425	1,627
Crude Oil Pipeline Services [Member] | Operating Segments [Member]
Revenue from contract with customer		47,554	61,523
Lease revenue
Total revenue for reportable segment		47,554	61,523
Crude Oil Pipeline Services [Member] | Third Party [Member]
Cost of product sales		14,221	24,587
Crude Oil Pipeline Services [Member] | Related Party [Member]
Cost of product sales		28,254	30,774
Crude Oil Terminalling Services [Member]
Total revenue for reportable segment		3,330	3,871
Operating expense, excluding depreciation and amortization		878	1,282
Operating margin, excluding depreciation and amortization		2,452	2,589
Total assets (end of period)		61,984	67,934
Crude Oil Terminalling Services [Member] | Operating Segments [Member]
Revenue from contract with customer		3,330	3,573
Lease revenue
Total revenue for reportable segment		3,330	3,573
Crude Oil Trucking Services [Member]
Total revenue for reportable segment		3,968	4,162
Operating expense, excluding depreciation and amortization		3,818	4,220
Operating margin, excluding depreciation and amortization		150	(58)
Total assets (end of period)		5,287	5,156
Crude Oil Trucking Services [Member] | Operating Segments [Member]
Revenue from contract with customer		2,543	2,833
Lease revenue
Total revenue for reportable segment		2,543	2,833
Service [Member] | Third Party [Member]
Revenue from contract with customer		13,229	15,886
Service [Member] | Related Party [Member]
Revenue from contract with customer		4,077	4,219
Service [Member] | Asphalt Terminalling Services [Member] | Third Party [Member]
Revenue from contract with customer		6,854	6,982
Service [Member] | Asphalt Terminalling Services [Member] | Related Party [Member]
Revenue from contract with customer		4,077	4,118
Service [Member] | Crude Oil Pipeline Services [Member] | Third Party [Member]
Revenue from contract with customer		502	2,498
Service [Member] | Crude Oil Pipeline Services [Member] | Related Party [Member]
Revenue from contract with customer			101
Service [Member] | Crude Oil Terminalling Services [Member] | Intersegment Eliminations [Member]
Revenue from contract with customer			298
Service [Member] | Crude Oil Terminalling Services [Member] | Third Party [Member]
Revenue from contract with customer		3,330	3,573
Service [Member] | Crude Oil Trucking Services [Member] | Intersegment Eliminations [Member]
Revenue from contract with customer		1,425	1,329
Service [Member] | Crude Oil Trucking Services [Member] | Third Party [Member]
Revenue from contract with customer		2,543	2,833
Product [Member] | Third Party [Member]
Revenue from contract with customer		47,052	58,924
Product [Member] | Crude Oil Pipeline Services [Member] | Third Party [Member]
Revenue from contract with customer		$ 47,052	$ 58,924

[1] The following table reconciles segment operating margin (excluding depreciation and amortization) to income before income taxes (in thousands): Three Months Ended March 31, 2019 2020 Operating margin, excluding depreciation and amortization $ 17,862 $ 17,570 Depreciation and amortization (6,734 ) (6,094 ) General and administrative expense (3,693 ) (3,464 ) Asset impairment expense (1,119 ) (5,122 ) Gain (loss) on sale of assets 1,724 (59 ) Other income - 558 Interest expense (4,271 ) (3,399 ) Income before income taxes $ 3,769 $ (10 )