Consolidated Statements of Cash Flows - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018
Cash flows from operating activities:
Net income (loss)	$ (2,168)	$ 11,578
Adjustments to reconcile net income (loss) to net cash provided by (used in) operating activities:
Depreciation	4,859	4,415
Amortization	1,935	1,897
Provision for losses on (recoveries of) accounts receivable	58	(34)
Stock-based compensation	5,369	2,871
Loss (gain) on disposal of property and equipment	(7)	11
Loss on debt extinguishment	0	12
Changes in operating assets and liabilities:
Accounts receivable, net	(2,836)	(8,382)
Inventory	(11,055)	(7,071)
Prepaid expenses and other current assets	2,590	(3,076)
Other assets	(2,670)	(1,405)
Accounts payable	3,290	1,517
Accrued and other long-term liabilities	(1,337)	(702)
Deferred revenues	(259)	(291)
Non-current income taxes payable	337	802
Net cash provided by (used in) operating activities	(1,894)	2,142
Cash flows from investing activities:
Purchases of property, equipment and patents	(10,007)	(8,654)
Proceeds from sale of property and equipment	19	8
Net cash used in investing activities	(9,988)	(8,646)
Cash flows from financing activities:
Principal payments on debt and capital leases	(67)	(17,300)
Net proceeds from debt financing	0	16,053
Proceeds from public offerings, net of offering costs	0	139,089
Proceeds from employee stock plan purchases	762	0
Proceeds from stock option exercises	1,032	161
Tax payments related to stock award issuances	(489)	0
Net cash provided by financing activities	1,238	138,003
Effect of exchange rate changes on cash	29	(4)
Net increase (decrease) in cash and cash equivalents	(10,615)	131,495
Cash and cash equivalents, beginning of period	149,478	36,687
Cash and cash equivalents, end of period	138,863	168,182
Supplemental disclosures:
Cash paid (received) for interest	(2,265)	802
Cash paid for income taxes	1,741	2,703
Accrued purchases of property, equipment and patents	1,275	709
Accrued deferred offering costs	$ 0	$ 830