Customer Concentrations

12 Months Ended

Dec. 31, 2017

Note 15—Customer Concentrations

We operate in multiple industry segments encompassing the construction of commercial, industrial, and public works infrastructure assets primarily throughout the United States. Typically, the top ten customers in any one calendar year generate revenues in excess of 50% of total revenues and consist of a different group of customers in each year.

During the years ended December 31, 2017, 2016 and 2015, we generated 38.4%, 45.6% and 48.9%, of our revenues, respectively, from the following customers (in thousands):


		2017			2016			2015
Description of Customer's Business	Segment	Amount		Percentage	Amount		Percentage	Amount		Percentage
State DOT	Civil	$	222,142	9.3%	$	193,049	9.7%	$	183,847	9.5%
Public gas and electric utility	Utilities		210,747	8.9%		184,002	9.2%		120,507	6.2%
Private gas and electric utility	Utilities		190,659	8.0%		201,443	10.1%		173,232	9.0%
Chemical/Energy producer	Power/Civil		160,995	6.8%		208,458	10.4%		173,931	9.0%
Pipeline operator	Pipeline		128,182	5.4%		*	*		*	*
Pipeline operator	Pipeline		*	*		123,055	6.2%		*	*
Pipeline operator	Pipeline		*	*		*	*		165,578	8.6%
Gas utility	Utilities		*	*		*	*		127,128	6.6%
		$	912,725	38.4%	$	910,007	45.6%	$	944,223	48.9%

(*)Indicates a customer with less than 5% of revenues during such period.

For the years ended December 31, 2017, 2016 and 2015, approximately 56.4%, 60.4% and 59.4%, respectively, of total revenues were generated from our top ten customers in that year. In each of the years, a different group of customers comprised the top ten customers by revenue.

At December 31, 2017, approximately 4.3% of our accounts receivable were due from one customer, and that customer provided 8.9% of our revenues for the year ended December 31, 2017. At December 31, 2016, approximately 20.8% of our accounts receivable were due from one customer, and that customer provided 6.2% of our revenues for the year ended December 31, 2016.