Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Cash Flows from Operating Activities
Net loss	$ (14,616)	$ (13,117)
Adjustments to reconcile net loss to net cash used in operating activities
Depreciation and amortization	380	276
Stock-based compensation	3,922	1,142
Amortization of debt issuance costs	235	165
Provision for doubtful accounts	514	0
Changes in operating assets and liabilities
Accounts receivable	(13,405)	(377)
Inventory	(3,571)	(1,391)
Prepaid expenses and other current assets	223	938
Other assets	228	(6)
Accounts payable	1,558	(1,334)
Accrued liabilities	936	114
Accrued compensation and benefits	128	567
Lease liability	161	(32)
Net cash used in operating activities	(23,307)	(13,055)
Cash Flows from Investing Activities
Purchases of property and equipment	(714)	(350)
Purchases of short-term investments	0	(10,298)
Proceeds from sales and maturities of short-term investments	12,592	14,697
Net cash provided by investing activities	11,878	4,049
Cash Flows from Financing Activities
Proceeds from exercise of stock options	344	44
Net cash provided by financing activities	344	44
Effect of exchange rate changes on cash and cash equivalents	(177)	(10)
Net decrease in cash and cash equivalents	(11,262)	(8,972)
Cash and cash equivalents, beginning of year	171,082	98,306
Cash and cash equivalents, end of period	159,820	89,334
Supplemental Disclosure of Cash Flow Information
Cash paid for interest	329	360
Cash paid for taxes	$ 0	$ 0