Note 17 - Business Segment Information - Segment Reporting Information (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020	Dec. 31, 2020
Total revenue	$ 669,913	$ 635,927
Gross profit	63,318	23,799
Depreciation, depletion and amortization	22,003	25,946
Segment assets	2,373,684	2,384,375	$ 2,379,996
Transportation [Member]
Total revenue	351,029	350,901
Gross profit	35,866	25,369
Depreciation, depletion and amortization	4,512	5,026
Water [Member]
Total revenue	99,753	101,657
Gross profit	8,566	9,347
Depreciation, depletion and amortization	7,280	9,564
Specialty [Member]
Total revenue	155,674	133,039
Gross profit	17,325	(10,719)
Depreciation, depletion and amortization	4,577	6,383
Materials [Member]
Total revenue	63,457	50,330
Gross profit	1,561	(198)
Depreciation, depletion and amortization	5,634	4,973
Operating Segments [Member]
Total revenue	685,605	650,249
Gross profit	63,318	23,799
Segment assets	896,736	1,074,853
Operating Segments [Member] | Transportation [Member]
Total revenue	351,029	350,901
Segment assets	297,663	304,376
Operating Segments [Member] | Water [Member]
Total revenue	99,753	101,657
Segment assets	130,185	275,447
Operating Segments [Member] | Specialty [Member]
Total revenue	155,674	133,039
Segment assets	106,534	128,471
Operating Segments [Member] | Materials [Member]
Total revenue	79,149	64,652
Segment assets	362,354	366,559
Consolidation, Eliminations [Member]
Total revenue	(15,692)	(14,322)
Consolidation, Eliminations [Member] | Transportation [Member]
Total revenue	0	0
Consolidation, Eliminations [Member] | Water [Member]
Total revenue	0	0
Consolidation, Eliminations [Member] | Specialty [Member]
Total revenue	0	0
Consolidation, Eliminations [Member] | Materials [Member]
Total revenue	$ (15,692)	$ (14,322)