Disaggregation of Revenue - Schedule of Disaggregation of Revenue (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Disaggregation Of Revenue [Line Items]
Total revenue	$ 789,540	$ 807,119	$ 1,409,341	$ 1,370,498
California [Member]
Disaggregation Of Revenue [Line Items]
Total revenue	234,987	257,990	361,088	467,889
Federal [Member]
Disaggregation Of Revenue [Line Items]
Total revenue	18,945	10,938	34,681	15,733
Heavy Civil [Member]
Disaggregation Of Revenue [Line Items]
Total revenue	80,390	198,076	279,895	381,162
Midwest [Member]
Disaggregation Of Revenue [Line Items]
Total revenue	67,717	82,601	121,750	154,883
Northwest [Member]
Disaggregation Of Revenue [Line Items]
Total revenue	251,243	216,965	354,837	305,356
Water and Mineral Services [Member]
Disaggregation Of Revenue [Line Items]
Total revenue	136,258	40,549	257,090	45,475
Transportation [Member]
Disaggregation Of Revenue [Line Items]
Total revenue	403,978	502,711	742,188	861,856
Transportation [Member] | California [Member]
Disaggregation Of Revenue [Line Items]
Total revenue	138,411	156,344	207,924	272,914
Transportation [Member] | Federal [Member]
Disaggregation Of Revenue [Line Items]
Total revenue	51	101	77	358
Transportation [Member] | Heavy Civil [Member]
Disaggregation Of Revenue [Line Items]
Total revenue	77,009	192,598	271,980	371,462
Transportation [Member] | Midwest [Member]
Disaggregation Of Revenue [Line Items]
Total revenue	28,135	22,113	46,196	38,455
Transportation [Member] | Northwest [Member]
Disaggregation Of Revenue [Line Items]
Total revenue	160,372	131,555	216,011	178,667
Transportation [Member] | Water and Mineral Services [Member]
Disaggregation Of Revenue [Line Items]
Total revenue	0	0	0	0
Water [Member]
Disaggregation Of Revenue [Line Items]
Total revenue	112,831	51,618	212,086	91,659
Water [Member] | California [Member]
Disaggregation Of Revenue [Line Items]
Total revenue	2,634	4,553	4,000	33,592
Water [Member] | Federal [Member]
Disaggregation Of Revenue [Line Items]
Total revenue	371	627	879	1,118
Water [Member] | Heavy Civil [Member]
Disaggregation Of Revenue [Line Items]
Total revenue	3,381	5,478	7,915	9,700
Water [Member] | Midwest [Member]
Disaggregation Of Revenue [Line Items]
Total revenue	0	1,020	84	1,516
Water [Member] | Northwest [Member]
Disaggregation Of Revenue [Line Items]
Total revenue	1,349	1,524	2,580	2,391
Water [Member] | Water and Mineral Services [Member]
Disaggregation Of Revenue [Line Items]
Total revenue	105,096	38,416	196,628	43,342
Specialty [Member]
Disaggregation Of Revenue [Line Items]
Total revenue	175,084	151,842	315,777	270,313
Specialty [Member] | California [Member]
Disaggregation Of Revenue [Line Items]
Total revenue	42,980	41,899	75,137	73,201
Specialty [Member] | Federal [Member]
Disaggregation Of Revenue [Line Items]
Total revenue	18,523	10,210	33,725	14,257
Specialty [Member] | Heavy Civil [Member]
Disaggregation Of Revenue [Line Items]
Total revenue	0	0	0	0
Specialty [Member] | Midwest [Member]
Disaggregation Of Revenue [Line Items]
Total revenue	39,582	59,468	75,470	114,912
Specialty [Member] | Northwest [Member]
Disaggregation Of Revenue [Line Items]
Total revenue	48,676	40,265	80,868	67,943
Specialty [Member] | Water and Mineral Services [Member]
Disaggregation Of Revenue [Line Items]
Total revenue	25,323	0	50,577	0
Materials [Member]
Disaggregation Of Revenue [Line Items]
Total revenue	97,647	100,948	139,290	146,670
Materials [Member] | California [Member]
Disaggregation Of Revenue [Line Items]
Total revenue	50,962	55,194	74,027	88,182
Materials [Member] | Federal [Member]
Disaggregation Of Revenue [Line Items]
Total revenue	0	0	0	0
Materials [Member] | Heavy Civil [Member]
Disaggregation Of Revenue [Line Items]
Total revenue	0	0	0	0
Materials [Member] | Midwest [Member]
Disaggregation Of Revenue [Line Items]
Total revenue	0	0	0	0
Materials [Member] | Northwest [Member]
Disaggregation Of Revenue [Line Items]
Total revenue	40,846	43,621	55,378	56,355
Materials [Member] | Water and Mineral Services [Member]
Disaggregation Of Revenue [Line Items]
Total revenue	$ 5,839	$ 2,133	$ 9,885	$ 2,133