Note 5 - Disaggregation of Revenue - Schedule of Disaggregation of Revenue (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Revenue	$ 3,445,606	$ 3,287,031	$ 2,958,374
Water and Mineral Services [Member]
Revenue	530,729	340,504	62,074
Transportation [Member]
Revenue	1,892,149	1,946,750	1,912,006
Transportation [Member] | Water and Mineral Services [Member]
Revenue	0	0	0
Water [Member]
Revenue	468,730	345,861	132,973
Water [Member] | Water and Mineral Services [Member]
Revenue	423,336	265,704	61,964
Specialty [Member]
Revenue	727,537	625,666	620,619
Specialty [Member] | Water and Mineral Services [Member]
Revenue	89,289	58,643	110
Materials [Member]
Revenue	357,190	368,754	292,776
Materials [Member] | Water and Mineral Services [Member]
Revenue	18,104	16,157	0
California 1[Member]
Revenue	992,100	1,017,638	848,687
California 1[Member] | Transportation [Member]
Revenue	581,074	607,737	470,996
California 1[Member] | Water [Member]
Revenue	25,005	52,757	39,071
California 1[Member] | Specialty [Member]
Revenue	187,556	143,471	160,572
California 1[Member] | Materials [Member]
Revenue	198,465	213,673	178,048
Federal [Member]
Revenue	85,703	44,270	38,486
Federal [Member] | Transportation [Member]
Revenue	688	683	31,406
Federal [Member] | Water [Member]
Revenue	1,171	2,116	1,884
Federal [Member] | Specialty [Member]
Revenue	83,844	41,471	5,196
Federal [Member] | Materials [Member]
Revenue	0	0	0
Heavy Civil [Member]
Revenue	687,344	808,194	761,003
Heavy Civil [Member] | Transportation [Member]
Revenue	671,923	788,722	738,576
Heavy Civil [Member] | Water [Member]
Revenue	13,215	19,472	22,427
Heavy Civil [Member] | Specialty [Member]
Revenue	2,206	0	0
Heavy Civil [Member] | Materials [Member]
Revenue	0	0	0
Midwest [Member]
Revenue	253,822	309,018	416,959
Midwest [Member] | Transportation [Member]
Revenue	100,235	84,523	60,007
Midwest [Member] | Water [Member]
Revenue	39	1,930	7,004
Midwest [Member] | Specialty [Member]
Revenue	153,548	222,565	349,948
Midwest [Member] | Materials [Member]
Revenue	0	0	0
Northwest [Member]
Revenue	895,908	767,407	831,165
Northwest [Member] | Transportation [Member]
Revenue	538,229	465,085	611,021
Northwest [Member] | Water [Member]
Revenue	5,964	3,882	623
Northwest [Member] | Specialty [Member]
Revenue	211,094	159,516	104,793
Northwest [Member] | Materials [Member]
Revenue	$ 140,621	$ 138,924	$ 114,728