Revenue (Tables)

9 Months Ended

Sep. 30, 2018

Revenue

Schedule of revenue by discipline

	Three months ended				Nine months ended
	September 30,				September 30,
	2018*		2017		2018*		2017
	(in thousands)				(in thousands)
Systems	$	56,394	$	69,218	$	215,789	$	186,908
Aftermarket		38,980		35,264		121,103		107,257
	$	95,374	$	104,482	$	336,892	$	294,165

Schedule of revenue by geographic markets

	Three months ended				Nine months ended
	September 30,				September 30,
	2018*		2017		2018*		2017
	(in thousands)				(in thousands)
North America	$	12,115	$	12,435	$	39,123	$	31,834
Asia		67,019		80,245		253,179		224,591
Europe		16,240		11,802		44,590		37,740
	$	95,374	$	104,482	$	336,892	$	294,165

Schedule of contract assets and contract liabilities

	September 30,		December 31,
	2018		2017
	(in thousands)
Contract assets	$	—	$	—
Contract liabilities	$	17,774	$	18,145

	Three months ended				Nine months ended
	September 30,				September 30,
	2018		2017		2018		2017
	(in thousands)
Revenue recognized in the period from:
Amounts included in contract liability at the beginning of the period	$	4,569	$	8,516	$	11,957	$	8,880
Performance obligations satisfied in previous periods	$	—	$	—	$	—	$	—