Segment, Geographic, Product and Significant Customer Information - Total Net Revenue (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 28, 2019	Sep. 29, 2018	Sep. 28, 2019	Sep. 29, 2018
Net revenues:
Total net revenues	$ 73,125	$ 76,590	$ 207,845	$ 247,507
United States [Member]
Net revenues:
Total net revenues	14,091	8,414	40,135	22,545
China [Member]
Net revenues:
Total net revenues	20,357	14,486	60,590	50,861
Japan [Member]
Net revenues:
Total net revenues	11,189	19,693	19,720	48,090
South Korea [Member]
Net revenues:
Total net revenues	10,519	23,598	37,557	92,397
Taiwan [Member]
Net revenues:
Total net revenues	8,590	1,883	23,529	4,918
Singapore [Member]
Net revenues:
Total net revenues	2,775	5,842	13,049	20,377
Other [Member]
Net revenues:
Total net revenues	$ 5,604	$ 2,674	$ 13,265	$ 8,319