Revenue (Tables)

12 Months Ended

Dec. 31, 2020

Revenue.

Schedule of revenue by discipline

	Year ended
	December 31,
	2020		2019		2018
	(in thousands)
Systems	$	293,624	$	202,571	$	280,388
CS&I/Aftermarket		180,936		140,387		162,187
Total Revenue	$	474,560	$	342,958	$	442,575

Schedule of revenue by geographic markets

	Year ended
	December 31,
	2020		2019		2018
	(in thousands)
North America	$	50,786	$	36,206	$	54,790
Asia Pacific		385,233		251,020		326,191
Europe		38,541		55,732		61,594
Total Revenue	$	474,560	$	342,958	$	442,575

Schedule of Contract liabilities

	Year ended
	December 31,
	2020		2019		2018
	(in thousands)
Balance, beginning of the period	$	29,251	$	22,584	$	18,145
Deferral of revenue		17,862		24,403		17,284
Recognition of deferred revenue		(24,055)		(17,736)		(12,845)
Balance, end of the period	$	23,058	$	29,251	$	22,584