Condensed Consolidated Statement of Stockholders' Equity (Unaudited) - USD ($) shares in Thousands	Total	Common Stock	Additional Paid-In Capital	Accumulated Deficit	Cumulative Translation Adjustments
Balance, shares at Dec. 31, 2018		55,089
Balance, amount at Dec. 31, 2018	$ 27,178,000	$ 55,000	$ 116,876,000	$ (89,753,000)	$ 0
Exercise of stock options, shares		128
Exercise of stock options, amount	271,000	$ 0	271,000	0	0
Net loss	(16,092,000)	$ 0	0	(16,092,000)	0
Share-based compensation, shares		167
Share-based compensation, amount	3,788,000	$ 0	3,788,000	0	0
Balance, shares at Jun. 30, 2019		55,384
Balance, amount at Jun. 30, 2019	15,145,000	$ 55,000	120,935,000	(105,845,000)	0
Balance, shares at Mar. 31, 2019		55,321
Balance, amount at Mar. 31, 2019	20,977,000	$ 55,000	119,012,000	(98,090,000)	0
Exercise of stock options, shares		63
Exercise of stock options, amount	164,000	$ 0	164,000	0	0
Share-based compensation	1,759,000	0	1,759,000	0	0
Net loss	(7,755,000)	$ 0	0	(7,755,000)	0
Balance, shares at Jun. 30, 2019		55,384
Balance, amount at Jun. 30, 2019	15,145,000	$ 55,000	120,935,000	(105,845,000)	0
Balance, shares at Dec. 31, 2019		59,562
Balance, amount at Dec. 31, 2019	20,445,000	$ 60,000	142,285,000	(121,900,000)	0
Issuance of common stock, net of offering costs of $0.1 million, shares		1,225
Issuance of common stock, net of offering costs of $0.1 million, amount	4,856,000	$ 1,000	4,855,000	0	0
Exercise of stock options, shares		634
Exercise of stock options, amount	2,312,000	$ 0	2,312,000	0	0
Share-based compensation	3,584,000	0	3,584,000	0	0
Translation adjustment	(3,000)	0	0	0	(3,000)
Net loss	(9,613,000)	$ 0	0	(9,613,000)	0
Balance, shares at Jun. 30, 2020		61,421
Balance, amount at Jun. 30, 2020	21,581,000	$ 61,000	153,036,000	(131,513,000)	(3,000)
Balance, shares at Mar. 31, 2020		59,605
Balance, amount at Mar. 31, 2020	16,548,000	$ 60,000	144,290,000	(127,802,000)	0
Issuance of common stock, net of offering costs of $0.1 million, shares		1,225
Issuance of common stock, net of offering costs of $0.1 million, amount	4,856,000	$ 1,000	4,855,000	0	0
Exercise of stock options, shares		591
Exercise of stock options, amount	2,180,000	$ 0	2,180,000	0	0
Share-based compensation	1,711,000	0	1,711,000	0	0
Translation adjustment	(3,000)	0	0	0	(3,000)
Net loss	(3,711,000)	$ 0	0	(3,711,000)	0
Balance, shares at Jun. 30, 2020		61,421
Balance, amount at Jun. 30, 2020	$ 21,581,000	$ 61,000	$ 153,036,000	$ (131,513,000)	$ (3,000)