The Company’s contracts contain both fixed-price and cost reimbursable components. Contract types are based on the component that represents the majority of the contract. The following table presents revenue disaggregated by contract type (in thousands):

	Three Months Ended
	March 31, 2020		March 31, 2019
Fixed-Price	$	308,308	$	257,695
Time-and-Materials		252,439		255,706
Cost-Plus		410,246		391,004
Total	$	970,993	$	904,405

See “Note 18 – Segments Information” for the Company’s revenues by business lines.

Contract assets and contract liabilities balances at March 31, 2020 and December 31, 2019 were as follows (in thousands):

	March 31, 2020		December 31, 2019
Contract assets	$	626,513	$	575,089
Contract liabilities		241,178		230,681
Net contract assets (liabilities) (1)	$	385,335	$	344,408

(1)

Total contract retentions included in net contract assets (liabilities) were $88.9 million as of March 31, 2020, of which $47.5 million are not expected to be paid in the next 12 months. Total contract retentions included in net contract assets (liabilities) were $85.5 million as of December 31,2019. Contract assets at March 31, 2020 and December 31, 2019 include $87.8 million and $73.0 million, respectively, related to unapproved change orders, claims, and requests for equitable adjustment. For the three months ended March 31, 2020 and March 31, 2019, there were no material losses recognized related to the collectability of claims, unapproved change orders, and requests for equitable adjustment.

During the three months ended March 31, 2020 and March 31, 2019, the Company recognized revenue of $94.3 million and $85.7 million, respectively, that was included in the corresponding contract liability balance at December 31, 2019 and December 31, 2018, respectively. The changes in contract assets and contract liabilities were the result of normal business activity and not significantly impacted by other factors, except as follows:

	March 31, 2020		December 31, 2019
Acquired contract assets	$	-	$	9,747
Acquired contract liabilities		-		1,300
Change in the estimate of variable consideration		-		12,166

There was no significant impairment of contract assets recognized during the three months ended March 31, 2020 and March 31, 2019.

There were no amounts due to revisions in estimates, such as changes in estimated claims or incentives, related to performance obligations partially satisfied in previous periods that individually had an impact of $5 million or more on revenue during the three months ended March 31, 2020 and March 31, 2019.

Accounts receivable, net consisted of the following as of March 31, 2020 and December 31, 2019 (in thousands):

	March 31, 2020			December 31, 2019
Billed	$	544,444		$	475,528
Unbilled		220,278			201,461
Total accounts receivable, gross		764,722			676,989
Allowance for doubtful accounts		(6,497	)		(5,497	)
Total accounts receivable, net	$	758,225		$	671,492

Billed accounts receivable represents amounts billed to clients that have not been collected. Unbilled accounts receivable represents amounts where the Company has a present contractual right to bill but an invoice has not been issued to the customer at the period-end date.

In connection with the adoption of ASU 2016-13, we have modified the historical presentation of gross receivables and the allowance for doubtful accounts to reflect only expected credit losses in the allowance in conformity with the current period presentation.

The allowance for doubtful accounts was determined based on consideration of trends in actual and forecasted credit quality of clients, including delinquency and payment history, type of client, such as a government agency or commercial sector client, and general economic conditions and particular industry conditions that may affect a client’s ability to pay. COVID-19 Impacts: We do not expect there to be a risk of non-payment with our government agency customers, but there is likely to be a delay in payments from our government agency customers in the Middle East. We generally don’t expect there to be a risk of non-payment from our commercial sector clients but do anticipate an unknown level of payment delays.

Transaction Price Allocated to the Remaining Unsatisfied Performance Obligations

The Company’s remaining unsatisfied performance obligations (“RUPO”) as of March 31, 2020 represent a measure of the total dollar value of work to be performed on contracts awarded and in-progress. The Company had $5.1 billion in RUPO as of March 31, 2020.

RUPO will increase with awards of new contracts and decrease as the Company performs work and recognizes revenue on existing contracts. Projects are included within RUPO at such time the project is awarded and agreement on contract terms has been reached. The difference between RUPO and backlog relates to unexercised option years that are included within backlog and the value of Indefinite Delivery/Indefinite Quantity (“IDIQ”) contracts included in backlog for which delivery orders have not been issued.

RUPO is comprised of: (a) original transaction price, (b) change orders for which written confirmations from our customers have been received, (c) pending change orders for which the Company expects to receive confirmations in the ordinary course of business, and (d) claim amounts that the Company has made against customers for which it has determined that it has a legal basis under existing contractual arrangements and a significant reversal of revenue is not probable, less revenue recognized to-date.

The Company expects to satisfy its RUPO as of March 31, 2020 over the following periods (in thousands):

Period RUPO Will Be Satisfied	Within One Year		Within One to Two Years		Thereafter
Federal Solutions	$	1,319,438	$	550,073	$	315,965
Critical Infrastructure		1,691,579		533,120		713,875
Total	$	3,011,017	$	1,083,193	$	1,029,840