Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Cash flows from operating activities:
Net loss	$ (8,857)	$ (63,509)	$ (42,758)
Adjustments to reconcile net loss to net cash provided by (used in) operating activities:
Depreciation and amortization	8,389	5,336	5,302
Stock-based compensation expense	37,674	10,953	8,206
Provision for doubtful accounts	876	104	336
Change in fair value of preferred stock warrant liability		40,333	(888)
Noncash interest expense	342	784	115
Loss from exit of facilities	1,120	525	3,804
Loss on disposals of property and equipment	8	54	29
Loss from extinguishment of debt		2,338
Write-off of deferred initial public offering costs			594
Impairment of long-lived assets	352		320
Amortization of premiums on short-term investments	(357)
Changes in operating assets and liabilities:
Accounts receivable	(50,673)	(41,184)	(26,354)
Inventories	(2,953)	10,828	(13,256)
Prepaid expenses and other current assets	(306)	(6,514)	(544)
Deferred cost of revenue	2,261	(1,959)	(2,885)
Other noncurrent assets	(732)	(2,794)	448
Accounts payable	(98)	24,315	(2,808)
Accrued liabilities	17,914	24,127	17,796
Other long-term liabilities	(1,101)	3,579	294
Deferred revenue	10,063	29,976	19,786
Net cash provided by (used in) operating activities	13,922	37,292	(32,463)
Cash flows from investing activities:
Purchase of property and equipment	(18,327)	(9,229)	(8,596)
Purchase of business, net of cash acquired		(2,959)
Purchases of short-term investments	(53,806)
Sales/maturities of short-term investments	12,000
Change in deposits		(80)	29
Net cash used in investing activities	(60,133)	(12,268)	(8,567)
Cash flows from financing activities:
Payments of costs related to initial public offering			(594)
Proceeds from borrowings, net		24,691	15,000
Repayments of borrowings		(40,446)	(15,000)
Holdback payment for a prior business acquisition	(500)
Proceeds from equity issued under incentive plans, net of repurchases	25,025	1,773	438
Proceeds from issuance of common stock pursuant to an initial public offering, net of issuance costs of $3.1 million		131,646
Net cash provided by financing activities	24,525	117,664	(156)
Net (Decrease) Increase in Cash	(21,686)	142,688	(41,186)
Cash and cash equivalents—Beginning of period	177,250	34,562	75,748
Cash and cash equivalents—End of period	155,564	177,250	34,562
Supplemental disclosures of cash flow information:
Cash paid for interest	493	1,149	236
Cash paid for income taxes	564	222	121
Supplemental disclosures of noncash investing and financing activities:
Unpaid portion of property and equipment purchases	$ 1,617	1,250	$ 306
Fair value of preferred stock warrants reclassified to additional paid in capital		52,355
Issuance of convertible preferred stock warrants in connection with debt		$ 2,032