Revenue (Tables)

12 Months Ended

Dec. 31, 2018

Revenue

Schedule of revenue by discipline

	Year ended
	December 31,
	2018*		2017		2016
	(in thousands)
Systems	$	280,388	$	262,688	$	139,284
Aftermarket		162,187		147,873		127,696
	$	442,575	$	410,561	$	266,980

Schedule of revenue by geographic markets

	Year ended
	December 31,
	2018*		2017		2016
	(in thousands)
North America	$	54,790	$	59,825	$	49,864
Asia Pacific		326,191		296,481		166,203
Europe		61,594		54,255		50,913
	$	442,575	$	410,561	$	266,980

Schedule of contract assets and contract liabilities

	December 31,		December 31,
	2018		2017
	(in thousands)
Contract assets	$	—	$	—
Contract liabilities	$	22,584	$	18,145

	Year ended
	December 31,
	2018		2017
Revenue recognized in the period from:
Amounts included in contract liability at the beginning of the period	$	12,845	$	9,522
Performance obligations satisfied in previous periods	$	—	$	—