Note 5 - Disaggregation of Revenue - Schedule of Disaggregation of Revenue (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Revenue	$ 1,088,110	$ 1,055,591	$ 2,497,451	$ 2,426,089
Water and Mineral Services [Member]
Revenue	151,781	147,222	408,871	192,697
California 1[Member]
Revenue	339,489	298,060	700,577	765,949
Federal [Member]
Revenue	24,184	13,912	58,865	29,645
Heavy Civil [Member]
Revenue	164,767	230,071	444,662	611,233
Midwest [Member]
Revenue	72,813	89,053	194,563	243,936
Northwest [Member]
Revenue	335,076	277,273	689,913	582,629
Transportation [Member]
Revenue	598,646	610,847	1,340,834	1,472,703
Transportation [Member] | Water and Mineral Services [Member]
Revenue	0	0	0	0
Transportation [Member] | California 1[Member]
Revenue	197,057	180,163	404,981	453,077
Transportation [Member] | Federal [Member]
Revenue	56	69	133	427
Transportation [Member] | Heavy Civil [Member]
Revenue	162,608	224,560	434,588	596,022
Transportation [Member] | Midwest [Member]
Revenue	27,359	23,346	73,555	61,801
Transportation [Member] | Northwest [Member]
Revenue	211,566	182,709	427,577	361,376
Water [Member]
Revenue	135,908	124,292	347,994	215,951
Water [Member] | Water and Mineral Services [Member]
Revenue	122,070	105,111	318,698	148,453
Water [Member] | California 1[Member]
Revenue	10,390	12,119	14,390	45,711
Water [Member] | Federal [Member]
Revenue	155	480	1,034	1,598
Water [Member] | Heavy Civil [Member]
Revenue	2,159	5,511	10,074	15,211
Water [Member] | Midwest [Member]
Revenue	39	194	123	1,710
Water [Member] | Northwest [Member]
Revenue	1,095	877	3,675	3,268
Specialty [Member]
Revenue	224,457	190,836	540,234	461,149
Specialty [Member] | Water and Mineral Services [Member]
Revenue	23,525	33,495	74,102	33,495
Specialty [Member] | California 1[Member]
Revenue	60,791	31,713	135,928	104,914
Specialty [Member] | Federal [Member]
Revenue	23,973	13,363	57,698	27,620
Specialty [Member] | Heavy Civil [Member]
Revenue	0	0	0	0
Specialty [Member] | Midwest [Member]
Revenue	45,415	65,513	120,885	180,425
Specialty [Member] | Northwest [Member]
Revenue	70,753	46,752	151,621	114,695
Materials [Member]
Revenue	129,099	129,616	268,389	276,286
Materials [Member] | Water and Mineral Services [Member]
Revenue	6,186	8,616	16,071	10,749
Materials [Member] | California 1[Member]
Revenue	71,251	74,065	145,278	162,247
Materials [Member] | Federal [Member]
Revenue	0	0	0	0
Materials [Member] | Heavy Civil [Member]
Revenue	0	0	0	0
Materials [Member] | Midwest [Member]
Revenue	0	0	0	0
Materials [Member] | Northwest [Member]
Revenue	$ 51,662	$ 46,935	$ 107,040	$ 103,290