Disaggregation of Revenue - Schedule of Disaggregation of Revenue (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Disaggregation Of Revenue [Line Items]
Total revenue	$ 619,801	$ 563,379
California [Member]
Disaggregation Of Revenue [Line Items]
Total revenue	126,101	209,899
Northwest [Member]
Disaggregation Of Revenue [Line Items]
Total revenue	103,594	88,391
Heavy Civil [Member]
Disaggregation Of Revenue [Line Items]
Total revenue	199,505	183,086
Federal [Member]
Disaggregation Of Revenue [Line Items]
Total revenue	15,736	4,795
Midwest [Member]
Disaggregation Of Revenue [Line Items]
Total revenue	54,033	72,282
Water and Mineral Services [Member]
Disaggregation Of Revenue [Line Items]
Total revenue	120,832	4,926
Transportation [Member]
Disaggregation Of Revenue [Line Items]
Total revenue	338,210	359,145
Transportation [Member] | California [Member]
Disaggregation Of Revenue [Line Items]
Total revenue	69,513	116,570
Transportation [Member] | Northwest [Member]
Disaggregation Of Revenue [Line Items]
Total revenue	55,639	47,112
Transportation [Member] | Heavy Civil [Member]
Disaggregation Of Revenue [Line Items]
Total revenue	194,971	178,864
Transportation [Member] | Federal [Member]
Disaggregation Of Revenue [Line Items]
Total revenue	26	257
Transportation [Member] | Midwest [Member]
Disaggregation Of Revenue [Line Items]
Total revenue	18,061	16,342
Transportation [Member] | Water and Mineral Services [Member]
Disaggregation Of Revenue [Line Items]
Total revenue	0	0
Water [Member]
Disaggregation Of Revenue [Line Items]
Total revenue	99,255	40,041
Water [Member] | California [Member]
Disaggregation Of Revenue [Line Items]
Total revenue	1,366	29,039
Water [Member] | Northwest [Member]
Disaggregation Of Revenue [Line Items]
Total revenue	1,231	867
Water [Member] | Heavy Civil [Member]
Disaggregation Of Revenue [Line Items]
Total revenue	4,534	4,222
Water [Member] | Federal [Member]
Disaggregation Of Revenue [Line Items]
Total revenue	508	491
Water [Member] | Midwest [Member]
Disaggregation Of Revenue [Line Items]
Total revenue	84	496
Water [Member] | Water and Mineral Services [Member]
Disaggregation Of Revenue [Line Items]
Total revenue	91,532	4,926
Specialty [Member]
Disaggregation Of Revenue [Line Items]
Total revenue	140,693	118,471
Specialty [Member] | California [Member]
Disaggregation Of Revenue [Line Items]
Total revenue	32,157	31,302
Specialty [Member] | Northwest [Member]
Disaggregation Of Revenue [Line Items]
Total revenue	32,192	27,678
Specialty [Member] | Heavy Civil [Member]
Disaggregation Of Revenue [Line Items]
Total revenue	0	0
Specialty [Member] | Federal [Member]
Disaggregation Of Revenue [Line Items]
Total revenue	15,202	4,047
Specialty [Member] | Midwest [Member]
Disaggregation Of Revenue [Line Items]
Total revenue	35,888	55,444
Specialty [Member] | Water and Mineral Services [Member]
Disaggregation Of Revenue [Line Items]
Total revenue	25,254	0
Materials [Member]
Disaggregation Of Revenue [Line Items]
Total revenue	41,643	45,722
Materials [Member] | California [Member]
Disaggregation Of Revenue [Line Items]
Total revenue	23,065	32,988
Materials [Member] | Northwest [Member]
Disaggregation Of Revenue [Line Items]
Total revenue	14,532	12,734
Materials [Member] | Heavy Civil [Member]
Disaggregation Of Revenue [Line Items]
Total revenue	0	0
Materials [Member] | Federal [Member]
Disaggregation Of Revenue [Line Items]
Total revenue	0	0
Materials [Member] | Midwest [Member]
Disaggregation Of Revenue [Line Items]
Total revenue	0	0
Materials [Member] | Water and Mineral Services [Member]
Disaggregation Of Revenue [Line Items]
Total revenue	$ 4,046	$ 0