

4.	REVENUE FROM CUSTOMERS

Backlog

The Company had the following backlog, by segment:



	March 31, 2020		December 31, 2019
Heavy Civil Backlog	$	886,575	$	834,049
Specialty Services Backlog	303,545		233,976
Total Heavy Civil and Specialty Services Backlog	$	1,190,120	$	1,068,025

The Company expects to recognize approximately 65% of its backlog as revenue during the next twelve months, and the balance thereafter.

Revenue Disaggregation

The following tables present the Company’s revenue disaggregated by major end market and contract type:



	Three Months Ended March 31,
Revenue by major end market	2020		2019
Heavy Highway	$	96,374	$	93,610
Aviation	28,457		29,937
Water Containment and Treatment	21,809		15,234
Other	8,975		11,724
Heavy Civil Revenue	$	155,615	$	150,505

Land Development	$	76,245	$	—
Commercial	28,478		30,679
Specialty Services Revenue	$	104,723	$	30,679

Residential Revenue	$	36,350	$	42,765

Revenues	$	296,688	$	223,949

Revenue by contract type
Fixed-Unit Price	$	141,739	$	141,219
Lump Sum	114,252		39,132
Residential and Other	40,697		43,598
Revenues	$	296,688	$	223,949

Each of these contract types presents advantages and disadvantages. Typically, the Company assumes more risk with lump-sum contracts. However, these types of contracts offer additional profits if the work is completed for less than originally estimated. Under fixed-unit price contracts, the Company’s profit may vary if actual labor-hour costs vary significantly from the negotiated rates. Also, because some contracts can provide little or no fee for managing material costs, the components of contract cost can impact profitability.

Variable Consideration

The Company has projects that it is in the process of negotiating, or awaiting final approval of, unapproved change orders and claims with its customers. The Company is proceeding with its contractual rights to recoup additional costs incurred from its customers based on completing work associated with change orders, including change orders with pending change order pricing, or claims related to significant changes in scope which resulted in substantial delays and additional costs in completing the work. Unapproved change order and claim information has been provided to the Company’s customers and negotiations with the customers are ongoing. If additional progress with an acceptable resolution is not reached, legal action will be taken.

Based upon the Company’s review of the provisions of its contracts, specific costs incurred and other related evidence supporting the unapproved change orders and claims, together in some cases as necessary with the views of the Company’s outside claim consultants, the Company concluded it was appropriate to include in project price amounts of $7,100 and $3,000, at March 31, 2020 and December 31, 2019, respectively. Provisions for estimated losses on uncompleted contracts are made in the period in which such losses are determined.

Contract Estimates

Accounting for long-term contracts and programs involves the use of various techniques to estimate total contract revenue and costs. For long-term contracts, the Company estimates the profit on a contract as the difference between the total estimated revenue and expected costs to complete a contract and recognizes such profit over the life of the contract.

Contract estimates are based on various assumptions to project the outcome of future events that often span several years. These assumptions include labor productivity and availability, the complexity of the work to be performed, the cost and availability of materials and the performance of subcontractors. Changes in job performance, job conditions and estimated profitability, including those changes arising from contract penalty provisions and final contract settlements may result in revisions to costs and income and are recognized in the period in which the revisions are determined.

Changes in estimated revenues and gross margin resulted in a net increase of $95 for the three months ended March 31, 2020, and net decrease of $200 for the three months ended March 31, 2019, included in “Operating income” on the Condensed Consolidated Statements of Operations.