Note 6 - Disaggregation of Revenue - Schedule of Disaggregation of Revenue (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Revenue	$ 1,065,189	$ 1,112,114	$ 2,616,887	$ 2,560,019
Water and Mineral Services [Member]
Revenue	109,428	152,047	318,398	409,137
Transportation [Member]
Revenue	623,999	623,867	1,510,001	1,407,577
Transportation [Member] \| Water and Mineral Services [Member]
Revenue	0	0	0	0
Water [Member]
Revenue	106,599	134,404	317,980	345,556
Water [Member] \| Water and Mineral Services [Member]
Revenue	85,331	122,336	259,690	318,964
Specialty [Member]
Revenue	205,134	224,744	513,087	538,497
Specialty [Member] \| Water and Mineral Services [Member]
Revenue	19,215	23,525	48,098	74,102
Materials [Member]
Revenue	129,457	129,099	275,819	268,389
Materials [Member] \| Water and Mineral Services [Member]
Revenue	4,882	6,186	10,610	16,071
California 1[Member]
Revenue	373,658	339,489	822,288	700,577
California 1[Member] \| Transportation [Member]
Revenue	224,636	197,057	478,590	404,981
California 1[Member] \| Water [Member]
Revenue	10,498	10,390	24,225	14,390
California 1[Member] \| Specialty [Member]
Revenue	62,623	60,791	158,076	135,928
California 1[Member] \| Materials [Member]
Revenue	75,901	71,251	161,397	145,278
Federal [Member]
Revenue	32,246	24,184	85,375	58,865
Federal [Member] \| Transportation [Member]
Revenue	3,140	56	5,306	133
Federal [Member] \| Water [Member]
Revenue	341	155	1,309	1,034
Federal [Member] \| Specialty [Member]
Revenue	28,765	23,973	78,760	57,698
Federal [Member] \| Materials [Member]
Revenue	0	0	0	0
Heavy Civil [Member]
Revenue	188,311	188,217	576,186	508,700
Heavy Civil [Member] \| Transportation [Member]
Revenue	165,434	187,828	519,963	501,330
Heavy Civil [Member] \| Water [Member]
Revenue	9,985	389	28,260	7,370
Heavy Civil [Member] \| Specialty [Member]
Revenue	12,892	0	27,963	0
Heavy Civil [Member] \| Materials [Member]
Revenue	0	0	0	0
Midwest [Member]
Revenue	68,288	73,099	177,776	192,826
Midwest [Member] \| Transportation [Member]
Revenue	43,896	27,359	103,081	73,555
Midwest [Member] \| Water [Member]
Revenue	0	39	152	123
Midwest [Member] \| Specialty [Member]
Revenue	24,392	45,701	74,543	119,148
Midwest [Member] \| Materials [Member]
Revenue	0	0	0	0
Northwest [Member]
Revenue	293,258	335,078	636,864	689,914
Northwest [Member] \| Transportation [Member]
Revenue	186,893	211,567	403,061	427,578
Northwest [Member] \| Water [Member]
Revenue	444	1,095	4,344	3,675
Northwest [Member] \| Specialty [Member]
Revenue	57,247	70,754	125,647	151,621
Northwest [Member] \| Materials [Member]
Revenue	$ 48,674	$ 51,662	$ 103,812	$ 107,040