Revenue (Tables)

6 Months Ended

Jun. 30, 2019

Revenue from Contract with Customer [Abstract]

Contract with Customer, Asset and Liability

The following table presents the beginning and ending balances of costs in excess of billings, billings in excess of cost and unearned revenue of June 30, 2019 and December 31, 2018, respectively, and revenue recognized during the six months ended June 30, 2019 and 2018, respectively, that was in billings in excess of cost and unearned revenue at the beginning of the period (in thousands):

	June 30, 2019			December 31, 2018
Costs in excess of billings	$	23,562		$	22,634
Billings in excess of cost	(38,133		)	(17,857		)
Unearned revenue	(9,971		)	(12,028		)

	Six Months Ended June 30, 2019		Six Months Ended June 30, 2018
Revenue recognized in the period from:
Amounts included in billings in excess of cost  at the beginning of the period	$	11,357	$	9,044
Amounts included in unearned revenue  at the beginning of the period	$	6,153	$	2,581