Construction Contracts

Construction contract costs and estimated earnings in excess of billings represent reimbursable costs and amounts earned under contracts in progress as of the balance sheet date. Such amounts become billable according to contract terms, which usually consider the passage of time, achievement of certain milestones, or completion of the project. The Company expects to bill and collect substantially all construction contract costs and estimated earnings in excess of billings as of December 31, 2018 during the year ending December 31, 2019.

Billings in excess of construction contract costs and estimated earnings represent billings or collections on contracts made in advance of revenue recognized.

The following table summarizes the changes to the balances in the Company’s construction contract costs and estimated earnings in excess of billings account and the billings in excess of construction contract costs and estimated earnings account for the year ended December 31, 2018 (in thousands):



	Construction contract costs and estimated earnings in excess of billings			Billings in excess of construction contract costs and estimated earnings
Balance as of January 1, 2018	$	245		$	3,591
Revenue recognized that was included in the balance at the beginning of the period	—			(3,591		)
Increases due to new billings, excluding amounts recognized as revenue during the period	—			4,243
Transferred to receivables	(245		)	—
Construction contract costs and estimated earnings not billed during the period	352			—
Changes due to cumulative catch-up adjustment arising from changes in the estimate of the stage of completion	1,006			(1,206		)
Balance as of December 31, 2018	$	1,358		$	3,037

The Company defers pre-contract costs when such costs are directly associated with specific anticipated contracts and their recovery is probable. Pre-contract costs of $1.4 million and $0.6 million were deferred as of December 31, 2018 and 2017, respectively. Amortization of pre-contract costs for the year ended December 31, 2018 totaled less than $0.1 million.

Construction receivables and payables include retentions—amounts that are generally withheld until the completion of the contract or the satisfaction of certain restrictive conditions such as fulfillment guarantees. As of December 31, 2018 and 2017, construction receivables included retentions of $8.5 million and $9.9 million, respectively. The Company expects to collect substantially all construction receivables as of December 31, 2018 during the year ending December 31, 2019. As of December 31, 2018 and 2017, construction payables included retentions of $21.6 million and $17.4 million, respectively. The Company expects to pay substantially all construction payables as of December 31, 2018 during the year ending December 31, 2019.

The Company’s net position on uncompleted construction contracts comprised the following as of December 31, 2018 and 2017 (in thousands):



	December 31,
	2018			2017
Costs incurred on uncompleted construction contracts	$	594,006		$	520,368
Estimated earnings	20,375			18,070
Billings	(616,060		)	(541,784		)
Net position	$	(1,679	)	$	(3,346	)



	December 31,
	2018			2017
Construction contract costs and estimated earnings in excess of billings	$	1,358		$	245
Billings in excess of construction contract costs and estimated earnings	(3,037		)	(3,591		)
Net position	$	(1,679	)	$	(3,346	)

The Company's balances and changes in construction contract price allocated to unsatisfied performance obligations (backlog) for each of the three years ended December 31, 2018 were as follows (in thousands):



	Years Ended December 31,
	2018			2017			2016
Beginning backlog	$	49,167		$	217,718		$	83,433
New contracts/change orders	192,852			25,224			293,115
Work performed	(76,156		)	(193,775		)	(158,830		)
Ending backlog	$	165,863		$	49,167		$	217,718

The Company expects to complete a majority of the uncompleted contracts as of December 31, 2018 during the next 12 to 18 months.