Consolidated Statements of Cash Flows - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
CASH FLOWS FROM OPERATING ACTIVITIES
Net loss	$ (24,816,000)	$ (21,653,000)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	840,000	721,000
Stock-based compensation	5,262,000	4,121,000
Non-cash warrant inducement expense	0	2,688,000
Non-cash interest and investment income	(153,000)	0
Non-cash patent write-off	96,000	0
(Gain) loss on sale of property and equipment	(7,000)	2,000
Changes in assets and liabilities:
Accounts receivable	(115,000)	6,000
Prepaids and other current assets	239,000	(376,000)
Other assets	(50,000)	(3,000)
Deferred taxes	(1,000)	(14,000)
Accounts payable	107,000	(143,000)
Accrued expenses	(66,000)	163,000
Accrued salaries and payroll related expenses	334,000	208,000
Deferred revenue	128,000	(184,000)
Deferred rent	71,000	(10,000)
Net cash used in operating activities	(18,131,000)	(14,474,000)
CASH FLOWS FROM INVESTING ACTIVITIES
Proceeds from sale of property and equipment	16,000	7,000
Purchases of property and equipment	(1,285,000)	(815,000)
Expenditures for patents and domain names	(219,000)	(332,000)
Redemptions of investments held-to-maturity	39,590,000	4,747,000
Purchases of investments held-to-maturity	(56,300,000)	0
Net cash provided by (used in) investing activities	(18,198,000)	3,607,000
CASH FLOWS FROM FINANCING ACTIVITIES
Net proceeds from the sale of common stock from private placement offerings	0	15,950,000
Net proceeds from the sale of common stock from underwritten public offering	21,190,000	0
Acquisition of common stock under Repurchase Program	(152,000)	0
Proceeds from exercises of warrants	260,000	9,272,000
Proceeds from exercises of stock options	14,000	78,000
Net cash provided by financing activities	21,312,000	25,300,000
Effects of currency translation on cash, cash equivalents and restricted cash	(2,000)	7,000
NET INCREASE IN CASH, CASH EQUIVALENTS AND RESTRICTED CASH	(15,019,000)	14,440,000
CASH, CASH EQUIVALENTS AND RESTRICTED CASH — Beginning of year	19,624,000	5,184,000
CASH, CASH EQUIVALENTS AND RESTRICTED CASH — End of year	4,605,000	19,624,000
SUPPLEMENTAL DISCLOSURE OF CASH FLOW INFORMATION
Cash paid for taxes	3,000	1,000
SUPPLEMENTAL DISCLOSURE OF NON-CASH ACTIVITIES
Common stock issued in settlement of accrued salaries and payroll related expenses	436,000	119,000
Stock options issued in settlement of liability	0	332,000
Property and equipment included in accounts payable	95,000	245,000
Property and equipment included in accrued liabilities	305,000	95,000
Noncash or Part Noncash Acquisition, Intangible Assets Acquired	39,000	9,000
Patents included in accounts payable	6,000	0
Total cash, cash equivalents and restricted cash	$ 19,624,000	$ 5,184,000