Contract Assets and Liabilities - Balance Sheet Classification (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Revenue from Contract with Customer [Abstract]
Costs and estimated earnings in excess of billings	$ 12,828	$ 19,256
Billings in excess of costs and estimated earnings	(11,235)	(77)
Costs and estimated earnings in excess of billings	1,593	19,179
Long-term contracts, loss accrual	$ 189	$ 322