CONSOLIDATED 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 income (loss)	$ (19,706)	$ 62,719	$ (5,062)
Adjustments to reconcile net income (loss) to net cash used in operating activities:
Gain on sale of the Core Business, net of tax	0	(68,404)	0
Depreciation and amortization	754	669	696
Provision for inventory obsolescence	132	0	0
Provision for product warranties	321	0	0
Loss on disposal of property and equipment	89	0	5
Stock based compensation	3,581	2,224	871
Change in fair value of derivative liabilities	0	(20)	(183)
Realized and unrealized gains on short term investments	(164)	(247)	0
Provision (benefit) for allowance for doubtful accounts	(163)	224	179
Benefit of deferred taxes	0	(368)	(196)
Changes in current assets and liabilities, net of effect of disposition:
Receivables	(3,970)	(447)	(303)
Prepaid expenses and other assets	(406)	(2,851)	(30)
Inventories	(2,367)	1,185	(368)
Accounts payable	1,054	(224)	(23)
Accrued expenses and other liabilities	2,370	(15,341)	710
Net cash used in operating activities	(18,475)	(20,881)	(3,704)
Cash flows from investing activities
Cash flows from investing activities	(1,301)	(363)	(624)
Proceeds from the disposition of Core business	0	91,095	0
Purchases of marketable securities	(18,884)	(87,189)	0
Proceeds of marketable securities	80,726	25,758	0
Net cash provided by (used in) investing activities	60,541	29,301	(624)
Cash flows from financing activities
Proceeds from stock option exercises	207	202	0
Repayment of finance lease liabilities	(60)	0	0
Repayment of mortgage note payable	0	(2,694)	(239)
Net cash provided by (used in) financing activities	147	(2,492)	(239)
Effect of exchange rates on cash	3	0	0
Net change in cash, cash equivalents and restricted cash	42,216	5,928	(4,567)
Cash, cash equivalents and restricted cash, beginning of period	16,596	10,668	15,235
Cash, cash equivalents and restricted cash, end of period	58,812	16,596	10,668
Cash paid for:
Interest expense	8	104	136
Income taxes	325	13,283	32
Non cash operating activities:
Transfer of other assets to fixed assets	42	0	0
Transfer of inventory to fixed assets	277	0	0
Non cash financing activities:
Cashless exercise of stock options/warrants	$ 612	$ 3,237	$ 557