REVENUE - Contract assets and the contract liabilities (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Changes in the contract assets and the contract liabilities
Costs incurred on uncompleted contracts	$ 214,887		$ 160,368
Earnings recognized on uncompleted contracts	30,902		28,581
Total	245,789		188,949
Less - billings to date	(241,263)		(184,009)
Net	4,526		4,940
Contract assets	7,225	$ 8,218	8,218
Contract liabilities	(2,699)	$ (3,278)	$ (3,278)
Revenue recognized from contracts in progress liability balance at December 31, 2019	$ 2,900