Revenues, Contract Assets and Contract Liabilities (Details Narrative) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Operating revenues:
Sales related to contract liabilities	$ 4,041	$ 2,306	$ 1,759	$ 1,086
Remaining performance obligation	$ 285,900		$ 285,900
Performance obligation, percentage	100.00%		100.00%
Performance obligation expected to be satisfied in the first year	$ 145,600		$ 145,600
Performance obligation expected to be satisfied in the second year	115,500		115,500
Performance obligation expected to be satisfied thereafter	$ 24,900		$ 24,900