Note 6 - Disaggregation of Revenue - Schedule of Disaggregation of Revenue (Details) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Revenue	$ 915,771	$ 866,092	$ 1,551,698	$ 1,447,905
Water and Mineral Services [Member]
Revenue	103,905	136,258	208,970	257,090
Transportation [Member]
Revenue	535,101	481,746	886,002	783,710
Transportation [Member] \| Water and Mineral Services [Member]
Revenue	0	0	0	0
Water [Member]
Revenue	109,724	112,070	211,381	211,152
Water [Member] \| Water and Mineral Services [Member]
Revenue	87,354	105,096	174,359	196,628
Specialty [Member]
Revenue	174,914	174,629	307,953	313,753
Specialty [Member] \| Water and Mineral Services [Member]
Revenue	13,433	25,323	28,883	50,577
Materials [Member]
Revenue	96,032	97,647	146,362	139,290
Materials [Member] \| Water and Mineral Services [Member]
Revenue	3,118	5,839	5,728	9,885
California 1[Member]
Revenue	270,431	234,989	448,630	361,088
California 1[Member] \| Transportation [Member]
Revenue	159,022	138,411	253,954	207,924
California 1[Member] \| Water [Member]
Revenue	8,215	2,634	13,727	4,000
California 1[Member] \| Specialty [Member]
Revenue	50,965	42,982	95,453	75,137
California 1[Member] \| Materials [Member]
Revenue	52,229	50,962	85,496	74,027
Federal [Member]
Revenue	25,859	18,944	53,129	34,681
Federal [Member] \| Transportation [Member]
Revenue	1,768	50	2,166	77
Federal [Member] \| Water [Member]
Revenue	587	371	968	879
Federal [Member] \| Specialty [Member]
Revenue	23,504	18,523	49,995	33,725
Federal [Member] \| Materials [Member]
Revenue	0	0	0	0
Heavy Civil [Member]
Revenue	209,853	156,380	387,875	320,483
Heavy Civil [Member] \| Transportation [Member]
Revenue	187,103	153,760	354,529	313,502
Heavy Civil [Member] \| Water [Member]
Revenue	11,173	2,620	18,275	6,981
Heavy Civil [Member] \| Specialty [Member]
Revenue	11,577	0	15,071	0
Heavy Civil [Member] \| Materials [Member]
Revenue	0	0	0	0
Midwest [Member]
Revenue	73,742	67,261	109,488	119,727
Midwest [Member] \| Transportation [Member]
Revenue	34,942	28,135	59,185	46,196
Midwest [Member] \| Water [Member]
Revenue	152	0	152	84
Midwest [Member] \| Specialty [Member]
Revenue	38,648	39,126	50,151	73,447
Midwest [Member] \| Materials [Member]
Revenue	0	0	0	0
Northwest [Member]
Revenue	231,981	252,260	343,606	354,836
Northwest [Member] \| Transportation [Member]
Revenue	152,266	161,390	216,168	216,011
Northwest [Member] \| Water [Member]
Revenue	2,243	1,349	3,900	2,580
Northwest [Member] \| Specialty [Member]
Revenue	36,787	48,675	68,400	80,867
Northwest [Member] \| Materials [Member]
Revenue	$ 40,685	$ 40,846	$ 55,138	$ 55,378