Commitments and Contingencies - Narrative (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jul. 01, 2018	Jul. 02, 2017	Jul. 01, 2018	Jul. 02, 2017	Dec. 31, 2017
Purchase Commitment, Excluding Long-term Commitment [Line Items]
Purchase obligations due within next twelve months	$ 1,300		$ 1,300
Total rent expense, net of sublease income	239	$ 210	$ 477	$ 421
Primary facility lease
Purchase Commitment, Excluding Long-term Commitment [Line Items]
Operating lease expiration date			2020-03
Wafer and finished goods inventory
Purchase Commitment, Excluding Long-term Commitment [Line Items]
Outstanding commitment for purchases	67		$ 67		$ 1,100
Other goods and services
Purchase Commitment, Excluding Long-term Commitment [Line Items]
Total outstanding purchase obligations	$ 1,600		$ 1,600