Income Taxes - Effective Tax Rate Differs from the Statutory Federal Income Tax Rate (Details)	12 Months Ended
	Dec. 30, 2017	Dec. 31, 2016	Jan. 02, 2016
Company's effective tax rate differs from the statutory federal income tax rate
Income tax provision at statutory rate	34.00%	34.00%	34.00%
State income taxes, net of federal benefit	2.40%	9.60%	(70.80%)
Permanent differences	0.00%	(1.50%)	12.00%
Research and development credits	0.60%	3.00%	(34.80%)
Change in valuation allowance	(34.90%)	(387.40%)
Foreign rate differential	(0.50%)
Other	(3.00%)	1.30%	(3.30%)
Effective tax rate	1.00%	(341.00%)	(62.90%)