Contract Assets and Liabilities - Activity (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Revenue from Contract with Customer [Abstract]
Costs incurred on uncompleted contracts	$ 110,624	$ 65,343
Estimated earnings	15,221	9,618
Total costs and estimated earnings	125,845	74,961
Less billings to date	(124,252)	(55,782)
Costs and estimated earnings in excess of billings	$ 1,593	$ 19,179