CONDENSED CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY (Unaudited) - USD ($) shares in Thousands, $ in Thousands	Total	Cumulative Effect, Period of Adoption, Adjustment	Common Stock	Additional paid-in capital	Shareholder note receivable	Treasury stock	Accumulated other comprehensive income (loss)	Accumulated deficit	Accumulated deficit Cumulative Effect, Period of Adoption, Adjustment
Balance at Dec. 31, 2019	$ 43,631	$ (81)	$ 6	$ 606,558	$ (5,000)	$ (97)	$ 1,088	$ (558,924)	$ (81)
Balance, shares at Dec. 31, 2019			61,400
Accounting Standards Update Extensible List	us-gaap:AccountingStandardsUpdate201908Member
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock-based compensation	$ 3,630			3,630
Distributor equity incentives	70			70
Common stock issued for warrant exercises	1,158			1,158
Common stock issued for warrant exercises, shares			1,390
Common stock issued for stock option exercises	83			83
Common stock issued for stock option exercises, shares			76
Common stock issued for vesting of restricted stock awards, net of shares retained for tax liability	(408)			(408)
Common stock issued for vesting of restricted stock awards, net of shares retained for tax liability, shares			394
Foreign currency translation adjustments	69						69
Net loss	(20,722)							(20,722)
Balance at Mar. 31, 2020	27,430		$ 6	611,091	(5,000)	(97)	1,157	(579,727)
Balance, shares at Mar. 31, 2020			63,260
Balance at Dec. 31, 2019	43,631	$ (81)	$ 6	606,558	(5,000)	(97)	1,088	(558,924)	$ (81)
Balance, shares at Dec. 31, 2019			61,400
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Foreign currency translation adjustments	75
Net loss	(36,527)
Balance at Jun. 30, 2020	18,822		$ 6	618,282	(5,000)	(97)	1,163	(595,532)
Balance, shares at Jun. 30, 2020			63,849
Balance at Mar. 31, 2020	27,430		$ 6	611,091	(5,000)	(97)	1,157	(579,727)
Balance, shares at Mar. 31, 2020			63,260
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock-based compensation	3,608			3,608
Distributor equity incentives	51			51
Common stock issued for employee stock purchase plan and stock option exercises	722			722
Common stock issued for employee stock purchase plan and stock option exercises, shares			202
Common stock issued for vesting of restricted stock awards, net of shares retained for tax liability	(164)			(164)
Common stock issued for vesting of restricted stock awards, net of shares retained for tax liability, shares			387
Issuance of common stock warrants, net	2,974			2,974
Foreign currency translation adjustments	6						6
Net loss	(15,805)							(15,805)
Balance at Jun. 30, 2020	18,822		$ 6	618,282	(5,000)	(97)	1,163	(595,532)
Balance, shares at Jun. 30, 2020			63,849
Balance at Dec. 31, 2020	129,880		$ 8	770,764	(4,000)	(97)	1,204	(637,999)
Balance, shares at Dec. 31, 2020			82,104
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock-based compensation	3,889			3,889
Distributor equity incentives	129			129
Common stock issued for warrant exercises	756			756
Common stock issued for warrant exercises, shares			2,019
Common stock issued for employee stock purchase plan and stock option exercises	210			210
Common stock issued for employee stock purchase plan and stock option exercises, shares			69
Common stock issued for vesting of restricted stock awards, net of shares retained for tax liability	(1,717)			(1,717)
Common stock issued for vesting of restricted stock awards, net of shares retained for tax liability, shares			379
Shareholder note receivable	1,100				1,100
Foreign currency translation adjustments	(3,052)						(3,052)
Net loss	(22,903)							(22,903)
Balance at Mar. 31, 2021	108,292		$ 8	774,031	(2,900)	(97)	(1,848)	(660,902)
Balance, shares at Mar. 31, 2021			84,571
Balance at Dec. 31, 2020	129,880		$ 8	770,764	(4,000)	(97)	1,204	(637,999)
Balance, shares at Dec. 31, 2020			82,104
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Foreign currency translation adjustments	(1,355)
Net loss	(61,108)
Balance at Jun. 30, 2021	213,514		$ 10	914,659	(1,800)	(97)	(151)	(699,107)
Balance, shares at Jun. 30, 2021			100,049
Balance at Mar. 31, 2021	108,292		$ 8	774,031	(2,900)	(97)	(1,848)	(660,902)
Balance, shares at Mar. 31, 2021			84,571
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock-based compensation	11,187			11,187
Distributor equity incentives	94			94
Common stock issued for warrant exercises	1,729			1,729
Common stock issued for warrant exercises, shares			1,576
Common stock issued for employee stock purchase plan and stock option exercises	1,479			1,479
Common stock issued for employee stock purchase plan and stock option exercises, shares			356
Common stock issued for vesting of performance and restricted stock awards, net of shares retained for tax liability	(5,687)			(5,687)
Common stock issued for vesting of performance and restricted stock awards, net of shares repurchased for tax liability, shares			1,125
Issuance of common stock for public offering, net of offering costs	131,828		$ 2	131,826
Issuance of common stock for public offering, net of offering costs, shares			12,421
Shareholder note receivable	1,100				1,100
Foreign currency translation adjustments	1,697						1,697
Net loss	(38,205)							(38,205)
Balance at Jun. 30, 2021	$ 213,514		$ 10	$ 914,659	$ (1,800)	$ (97)	$ (151)	$ (699,107)
Balance, shares at Jun. 30, 2021			100,049