Note 19 - Business Segment Information - Segment Reporting Information (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2019
Total revenue	$ 915,771	$ 866,092	$ 1,551,698	$ 1,447,905
Gross (loss) profit	88,343	46,758	112,142	47,896
Assets, Total	2,508,654	2,524,617	2,508,654	2,524,617	$ 2,502,088
Transportation [Member]
Total revenue	535,101	481,746	886,002	783,710
Gross (loss) profit	31,197	499	56,566	(15,849)
Depreciation, depletion and amortization	4,391	4,845	9,417	8,485
Water [Member]
Total revenue	109,724	112,070	211,381	211,152
Gross (loss) profit	12,579	10,502	21,926	18,448
Depreciation, depletion and amortization	9,577	10,931	19,141	21,987
Specialty [Member]
Total revenue	174,914	174,629	307,953	313,753
Gross (loss) profit	25,280	21,755	14,561	35,053
Depreciation, depletion and amortization	6,737	8,401	13,120	14,213
Materials [Member]
Total revenue	96,032	97,647	146,362	139,290
Gross (loss) profit	19,287	14,002	19,089	10,244
Depreciation, depletion and amortization	5,470	6,054	10,443	11,633
Operating Segments [Member]
Total revenue	961,597	921,788	1,611,846	1,512,514
Gross (loss) profit	88,343	46,758	112,142	47,896
Depreciation, depletion and amortization	26,175	30,231	52,121	56,318
Assets, Total	1,073,487	1,157,277	1,073,487	1,157,277
Operating Segments [Member] | Transportation [Member]
Total revenue	535,101	481,746	886,002	783,710
Assets, Total	304,312	329,140	304,312	329,140
Operating Segments [Member] | Water [Member]
Total revenue	109,724	112,070	211,381	211,152
Assets, Total	267,385	302,143	267,385	302,143
Operating Segments [Member] | Specialty [Member]
Total revenue	174,914	174,629	307,953	313,753
Assets, Total	123,881	146,346	123,881	146,346
Operating Segments [Member] | Materials [Member]
Total revenue	141,858	153,343	206,510	203,899
Assets, Total	377,909	379,648	377,909	379,648
Consolidation, Eliminations [Member]
Total revenue	(45,826)	(55,696)	(60,148)	(64,609)
Consolidation, Eliminations [Member] | Transportation [Member]
Total revenue	0	0	0	0
Consolidation, Eliminations [Member] | Water [Member]
Total revenue	0	0	0	0
Consolidation, Eliminations [Member] | Specialty [Member]
Total revenue	0	0	0	0
Consolidation, Eliminations [Member] | Materials [Member]
Total revenue	$ (45,826)	$ (55,696)	$ (60,148)	$ (64,609)