Note 21 - Reportable Segment Information - Segment Reporting Information (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2021	Sep. 30, 2021	Jun. 30, 2021	Mar. 31, 2021	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Total revenue	$ 683,196	$ 925,854	$ 834,671	$ 566,332	$ 830,390	$ 955,761	$ 811,866	$ 530,862	$ 3,010,053	$ 3,128,879	$ 2,914,877
Range of increase in gross profit from each project, net	51,652	$ 101,960	$ 98,232	$ 53,712	93,319	$ 113,015	$ 81,048	$ 17,271	305,556	304,653	189,785
Segment assets	2,494,927				2,379,996				2,494,927	2,379,996
Transportation [Member]
Total revenue									2,602,306	2,764,094	2,575,791
Range of increase in gross profit from each project, net									248,350	241,444	146,472
Depreciation, depletion and amortization									32,691	33,155	32,857
Water [Member]
Total revenue									407,747	364,785	339,086
Range of increase in gross profit from each project, net									57,206	63,209	43,313
Depreciation, depletion and amortization									24,905	21,198	22,292
Specialty [Member]
Total revenue									3,010,053	3,128,879	2,914,877
Range of increase in gross profit from each project, net									305,556	304,653	189,785
Depreciation, depletion and amortization									57,596	54,353	55,149
Operating Segments [Member]
Segment assets	691,650				687,643				691,650	687,643
Operating Segments [Member] | Transportation [Member]
Total revenue									2,602,306	2,764,094	2,575,791
Segment assets	358,561				371,479				358,561	371,479
Operating Segments [Member] | Water [Member]
Total revenue									552,548	513,546	490,098
Segment assets	333,089				316,164				333,089	316,164
Operating Segments [Member] | Specialty [Member]
Total revenue									3,154,854	3,277,640	3,065,889
Segment assets	$ 691,650				$ 687,643				691,650	687,643
Consolidation, Eliminations [Member] | Transportation [Member]
Total revenue									0	0	0
Consolidation, Eliminations [Member] | Water [Member]
Total revenue									(144,801)	(148,761)	(151,012)
Consolidation, Eliminations [Member] | Specialty [Member]
Total revenue									$ (144,801)	$ (148,761)	$ (151,012)