Segment, Geographic, Product and Significant Customer Information - Revenue Net (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 29, 2018	Sep. 30, 2017	Sep. 29, 2018	Sep. 30, 2017
Net revenues:
Total net revenues	$ 76,590	$ 56,675	$ 247,507	$ 180,416
South Korea [Member]
Net revenues:
Total net revenues	23,598	22,269	92,397	72,388
Japan [Member]
Net revenues:
Total net revenues	19,693	4,781	48,090	17,400
United States [Member]
Net revenues:
Total net revenues	8,414	6,231	22,545	28,101
China [Member]
Net revenues:
Total net revenues	14,486	3,403	50,861	17,420
Taiwan [Member]
Net revenues:
Total net revenues	1,883	2,304	4,918	19,016
Singapore [Member]
Net revenues:
Total net revenues	5,842	9,774	20,377	12,229
Other [Member]
Net revenues:
Total net revenues	$ 2,674	$ 7,913	$ 8,319	$ 13,862