Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	9 Months Ended
	Oct. 01, 2017	Sep. 25, 2016
Cash flows from operating activities
Net loss	$ 2,087	$ (1,927)
Adjustments to reconcile net income (loss) to net cash provided by operating activities:
Depreciation and amortization	1,566	880
Stock-based compensation expense	7,447	2,224
Accretion of discount on investments	93	0
Non-cash interest expense, net	254	140
Change in fair value of convertible preferred stock warrants liability	0	109
Changes in assets and liabilities:
Accounts receivable	(8,340)	(1,589)
Inventory	(7,880)	(2,861)
Prepaid expenses and other current assets	(22)	(283)
Deferred rent and other assets	(790)	16
Accounts payable	5,119	(1,136)
Accrued liabilities and other current liabilities	14,660	6,136
Net cash provided by operating activities	14,194	1,709
Cash flows from investing activities
Purchase of property and equipment	(6,961)	(1,621)
Purchase of marketable securities	(104,044)	0
Proceeds from sales of marketable securities	3,670	0
Maturities of marketable securities	12,239	0
Restricted cash	0	(1,559)
Net cash used in investing activities	(95,096)	(3,180)
Cash flows from financing activities
Proceeds from issuance of common stock	4,553	785
Payments of offering costs	(96)	(881)
Proceeds from revolving line of credit, net of fees paid	0	2,950
Repayment of revolving line of credit	0	(3,000)
Proceeds from issuance of long-term debt, net of fees paid	0	3,854
Repayments of long-term debt	(1,756)	(3,265)
Net cash provided by financing activities	2,701	443
Net decrease in cash and cash equivalents	(78,201)	(1,028)
Beginning of period	117,045	18,850
End of period	38,844	17,822
Supplemental disclosure of cash flow information
Interest paid during the period	342	419
Income taxes paid during the period	746	87
Supplemental disclosure of non-cash investing and financing activities
Unpaid offering costs	254	1,396
Purchases of property and equipment included in accounts payable and accrued liabilities and other current liabilities	280	18
Issuance of warrants in conjunction with the execution of debt agreement	$ 0	$ 96