Revenue (Tables)

3 Months Ended

Mar. 31, 2018

Revenue

Schedule of revenue by discipline

	Three months ended
	March 31,
	2018*		2017
	(in thousands)
Systems	$	85,475	$	55,249
Aftermarket		36,710		31,644
	$	122,185	$	86,893

Schedule of revenue by geographic markets

	Three months ended
	March 31,
	2018*		2017
	(in thousands)
North America	$	10,523	$	6,997
Asia		97,689		63,245
Europe		13,973		16,651
	$	122,185	$	86,893

Schedule of contract assets and contract liabilities

	March 31,		December 31,		March 31,
	2018		2017		2017
	(in thousands)
Contract assets	$	—	$	—	$	—
Contract liabilities	$	18,522	$	18,145	$	13,121
Revenue recognized in the period from:
Amounts included in contract liability at the beginning of the period	$	6,342	$	9,105	$	5,277
Performance obligations satisfied in previous periods	$	—	$	—	$	—