Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Cash flows from operating activities:
Net loss available to common stockholders	$ (12,443)	$ (29,886)	$ (30,384)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	8,106	4,921	3,181
Non-cash expenses related to convertible note	0	0	1,123
Share-based compensation expense	12,807	2,241	665
Loss on sale of fixed assets	93	76	0
Amortization of debt issuance costs	181	109	37
Change in preferred and common stock warrant liabilities	12,503	1,120	385
Restructuring loss on write-off of fixed assets	0	0	2,302
Net change in operating assets and liabilities:
Accounts receivable	(27,454)	(9,045)	(2,702)
Inventories	(51,339)	(22,113)	(1,959)
Prepaid expenses and other assets	(2,362)	325	(795)
Accounts payable	10,149	10,455	2,361
Accrued expenses and other current liabilities	2,743	3,798	464
Long-term liabilities	21	278	49
Net cash used in operating activities	(46,995)	(37,721)	(25,273)
Cash flows used in investing activities:
Purchases of property, plant and equipment	(23,795)	(22,228)	(7,908)
Proceeds from sale of fixed assets	0	67	0
Purchases of property, plant and equipment held for sale	(2,123)	(1,022)	0
Proceeds from sale of assets held for sale	299	0	0
Payment of security deposits	(545)	(59)	(207)
Net cash used in investing activities	(26,164)	(23,242)	(8,115)
Cash flows from financing activities:
Proceeds from issuance of common stock pursuant to the initial public offering, net of issuance costs	254,868	0	0
Proceeds from issuance of common stock pursuant to the secondary public offering, net of issuance costs	37,394	0	0
Proceeds from convertible note issuance	0	0	10,000
Proceeds from revolving credit line	0	6,000	2,500
Proceeds from term loan borrowing	0	20,000	0
Proceeds from equipment loan borrowing	0	5,000	0
Proceeds from payoff of notes receivable for restricted stock purchase	0	951	0
Repayments on revolving credit line	0	(2,500)	0
Repayment on term loan	0	(1,000)	(500)
Repayment of Missouri Note	0	(1,450)	0
Payments of capital lease obligations	(55)	(153)	(221)
Proceeds from exercise of stock options	2,669	1,369	379
Proceeds from restricted stock exercise	0	2	0
Payments of deferred offering costs	0	(2,415)	0
Debt issuance costs	0	(437)	0
Payment for repurchase of common stock	0	(514)	0
Net cash provided by financing activities	294,876	76,199	55,425
Net increase in cash and cash equivalents	221,717	15,236	22,037
Cash and cash equivalents at the beginning of the period	54,271	39,035	16,998
Cash and cash equivalents at the end of the period	275,988	54,271	39,035
Cash paid during the period for:
Interest	3,019	924	269
Taxes	9	4	3
Non-cash investing and financing activities:
Capital lease obligations for the purchase of property, plant and equipment	225	85	35
Issuance of convertible preferred stock warrants in connection with debt	0	248	0
Non-cash additions to property, plant and equipment	1,418	1,146	1,376
Offering costs, accrued not yet paid	0	745	0
Reclassification of warrant liability to additional paid-in capital upon closing of the initial public offering	14,421	0	0
Conversion of convertible preferred stock to common stock upon initial public offering	199,540	0	0
Series H
Cash flows from financing activities:
Proceeds from preferred stock offering, net of offering costs	0	49,999	0
Series G
Cash flows from financing activities:
Proceeds from preferred stock offering, net of offering costs	0	1,347	43,188
Series F
Cash flows from financing activities:
Proceeds from preferred stock offering, net of offering costs	$ 0	$ 0	$ 79