5. Disaggregation of Revenue

We disaggregate our revenue based on our reportable segments and operating groups as it is the format that is regularly reviewed by management. Our reportable segments are: Transportation, Water, Specialty and Materials. Our operating groups are: (i) California; (ii) Northwest; (iii) Heavy Civil; (iv) Federal (formerly included with Heavy Civil); (v) Midwest (formerly Kenny less the underground business); and (vi) Water and Mineral Services (which includes LiquiForce, Layne and the underground business of the former Kenny operating group). The following tables present our disaggregated revenue (in thousands):

Three Months Ended September 30,

	Transportation		Water		Specialty		Materials		Total
2018
California	$	180,163	$	12,119	$	31,713	$	74,065	$	298,060
Northwest		182,709		877		46,752		46,935		277,273
Heavy Civil		224,560		5,511		—		—		230,071
Federal		69		480		13,363		—		13,912
Midwest		23,346		194		65,513		—		89,053
Water and Mineral Services		—		105,111		33,495		8,616		147,222
Total	$	610,847	$	124,292	$	190,836	$	129,616	$	1,055,591

2017
California	$	153,941	$	12,559	$	51,191	$	54,971	$	272,662
Northwest		245,875		51		23,477		43,164		312,567
Heavy Civil		201,951		8,066		—		—		210,017
Federal		8,170		641		1,062		—		9,873
Midwest		14,790		1,400		122,156		—		138,346
Water and Mineral Services		—		13,661		—		—		13,661
Total	$	624,727	$	36,378	$	197,886	$	98,135	$	957,126

Nine Months Ended September 30,

	Transportation		Water		Specialty		Materials		Total
2018
California	$	453,077	$	45,711	$	104,914	$	162,247	$	765,949
Northwest		361,376		3,268		114,695		103,290		582,629
Heavy Civil		596,022		15,211		—		—		611,233
Federal		427		1,598		27,620		—		29,645
Midwest		61,801		1,710		180,425		—		243,936
Water and Mineral Services		—		148,453		33,495		10,749		192,697
Total	$	1,472,703	$	215,951	$	461,149	$	276,286	$	2,426,089

2017
California	$	331,329	$	26,017	$	112,883	$	127,850	$	598,079
Northwest		470,254		530		76,821		83,984		631,589
Heavy Civil		551,856		18,737		—		—		570,593
Federal		28,846		1,579		2,417		—		32,842
Midwest		41,111		5,707		260,035		—		306,853
Water and Mineral Services		—		48,374		109		—		48,483
Total	$	1,423,396	$	100,944	$	452,265	$	211,834	$	2,188,439