Condensed Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2017	Oct. 01, 2016
Cash flows from operating activities:
Net loss	$ (70,450)	$ (45,985)
Adjustments to reconcile net loss to net cash provided by (used in) operating activities:
Depreciation and amortization	3,883	4,201
Impairment of assets		320
Stock-based compensation expense	7,517	6,016
Provision for doubtful accounts	17	278
Change in fair value of preferred stock warrant liability	40,333	(1,087)
Noncash interest expense	668	89
Loss on disposals of property and equipment	54	29
Loss from exit of facilities	232	3,804
Write-off of deferred initial public offering costs		594
Changes in operating assets and liabilities:
Due from related parties	(5)	165
Accounts receivable	(5,532)	(4,058)
Inventories	8,118	(19,738)
Prepaid expenses and other current assets	(2,867)	385
Deferred cost of revenue	(972)	(1,759)
Other noncurrent assets	(5,870)	445
Accounts payable	17,406	13,137
Accrued liabilities	17,662	20,193
Other long-term liabilities	4,410	959
Deferred revenue	16,588	9,102
Net cash provided by (used in) operating activities	31,192	(12,910)
Cash flows from investing activities:
Purchase of property and equipment	(6,671)	(7,380)
Purchase of business, net of cash acquired	(2,959)
Restricted cash	31	29
Net cash used in investing activities	(9,599)	(7,351)
Cash flows from financing activities:
Payments of costs related to initial public offering		(594)
Proceeds from borrowings, net	24,691
Repayments of borrowings	(15,000)	(15,000)
Proceeds from exercise of stock options, net of repurchases	1,072	366
Net cash provided by (used in) financing activities	10,763	(15,228)
Net Increase (Decrease) In Cash	32,356	(35,489)
Cash—Beginning of period	34,562	75,748
Cash—End of period	66,918	40,259
Supplemental disclosures of cash flow information:
Cash paid for interest	583	149
Cash paid for income taxes	162	132
Supplemental disclosures of noncash investing and financing activities:
Purchases of property and equipment recorded in accounts payable and accrued liabilities	836	$ 671
Issuance of convertible preferred stock warrants in connection with debt	2,032
Unpaid initial public offering costs	$ 2,992