Condensed Consolidated Statements of Stockholders' Deficit - USD ($) $ in Thousands	Total	Convertible Note Mann Group	June 2020 Note	Convertible Note Interest Mann Group	2024 Convertible Notes	2024 Convertible Note Interest	At-the-market Offering	Common Stock	Common Stock Convertible Note Mann Group	Common Stock June 2020 Note	Common Stock Convertible Note Interest Mann Group	Common Stock 2024 Convertible Notes	Common Stock 2024 Convertible Note Interest	Common Stock At-the-market Offering	Additional Paid-in Capital	Additional Paid-in Capital Convertible Note Mann Group	Additional Paid-in Capital June 2020 Note	Additional Paid-in Capital Convertible Note Interest Mann Group	Additional Paid-in Capital 2024 Convertible Notes	Additional Paid-in Capital 2024 Convertible Note Interest	Additional Paid-in Capital At-the-market Offering	Accumulated Other Comprehensive Income (Loss)	Accumulated Deficit
Beginning Balance at Dec. 31, 2019	$ (190,526)							$ 2,118							$ 2,799,278							$ (19)	$ (2,991,903)
Beginning Balance (in shares) at Dec. 31, 2019								211,788,000
Net issuance of common stock associated with stock options and restricted stock units	(317)							$ 5							(322)
Net issuance of common stock associated with stock options and restricted stock units (in shares)								504,000
Issuance of common stock under Employee Stock Purchase Plan	318							$ 3							315
Issuance of common stock under Employee Stock Purchase Plan (in shares)								334,000
Stock-based compensation expense	1,128														1,128
Issuance of common stock associated with debt interest payment	144							$ 1							143
Issuance of common stock associated with debt interest payment (in shares)								99,000
Issuance of common stock							$ 522							$ 4							$ 518
Issuance of common stock (in shares)														413,000
Issuance cost associated with at-the-market offering	(16)														(16)
Write-off of cumulative translation loss	19																					19
Net loss	(9,322)																						(9,322)
Ending Balance at Mar. 31, 2020	(198,050)							$ 2,131							2,801,044								(3,001,225)
Ending Balance (in shares) at Mar. 31, 2020								213,138,000
Beginning Balance at Dec. 31, 2019	(190,526)							$ 2,118							2,799,278							$ (19)	(2,991,903)
Beginning Balance (in shares) at Dec. 31, 2019								211,788,000
Issuance of common stock under Employee Stock Purchase Plan (in shares)								333,727
Net loss	(19,574)
Ending Balance at Jun. 30, 2020	(179,710)							$ 2,289							2,829,478								(3,011,477)
Ending Balance (in shares) at Jun. 30, 2020								228,928,000
Beginning Balance at Mar. 31, 2020	(198,050)							$ 2,131							2,801,044								(3,001,225)
Beginning Balance (in shares) at Mar. 31, 2020								213,138,000
Net issuance of common stock associated with stock options and restricted stock units	117							$ 3							114
Net issuance of common stock associated with stock options and restricted stock units (in shares)								297,000
Stock-based compensation expense	2,185														2,185
Issuance of common stock from the exercise of warrants	11,600							$ 73							11,527
Issuance of common stock from the exercise of warrants (in Share)								7,250,000
Issuance of common stock pursuant to conversion notes			$ 2,630							$ 12							$ 2,618
Issuance of common stock pursuant to conversion notes (in shares)										1,235,000
Issuance of common stock							12,366							$ 75							12,291
Issuance of common stock (in shares)														7,459,000
Issuance cost associated with at-the-market offering	(320)														(320)
Issuance of common stock from market price stock purchase	14														14
Issuance of common stock under Market Price Stock Purchase Plan (in shares)								10,000
Adjustment of common stock in association with restricted stock units								$ (5)							5
Adjustment of common stock in association with restricted stock units (in shares)								(461,000)
Net loss	(10,252)																						(10,252)
Ending Balance at Jun. 30, 2020	(179,710)							$ 2,289							2,829,478								(3,011,477)
Ending Balance (in shares) at Jun. 30, 2020								228,928,000
Beginning Balance at Dec. 31, 2020	(180,419)							$ 2,421							2,866,303								(3,049,143)
Beginning Balance (in shares) at Dec. 31, 2020								242,118,000
Net issuance of common stock associated with stock options and restricted stock units	397							$ 4							393
Net issuance of common stock associated with stock options and restricted stock units (in shares)								390,000
Issuance of common stock under Employee Stock Purchase Plan	390							$ 3							387
Issuance of common stock under Employee Stock Purchase Plan (in shares)								293,000
Stock-based compensation expense	1,935														1,935
Issuance of common stock pursuant to conversion notes		$ 9,573		$ 427	$ 5,000				$ 38		$ 2	$ 17				$ 9,535		$ 425	$ 4,983
Issuance of common stock pursuant to conversion notes (in shares)									3,830,000		170,000	1,667,000
Issuance of common stock pursuant to payoff of the 2024 convertible note interest						$ 143														$ 143
Issuance of common stock pursuant to payoff of the 2024 convertible note interest (in shares)													27,000
Issuance of common stock							$ 1,886							$ 6							$ 1,880
Issuance of common stock (in shares)														578,000
Issuance cost associated with at-the-market offering	(38)														(38)
Net loss	(12,916)																						(12,916)
Ending Balance at Mar. 31, 2021	(173,622)							$ 2,491							2,885,946								(3,062,059)
Ending Balance (in shares) at Mar. 31, 2021								249,073,000
Beginning Balance at Dec. 31, 2020	(180,419)							$ 2,421							2,866,303								(3,049,143)
Beginning Balance (in shares) at Dec. 31, 2020								242,118,000
Issuance of common stock under Employee Stock Purchase Plan (in shares)								292,981
Net loss	(48,439)
Ending Balance at Jun. 30, 2021	(183,551)							$ 2,496							2,911,535								(3,097,582)
Ending Balance (in shares) at Jun. 30, 2021								249,618,000
Beginning Balance at Mar. 31, 2021	(173,622)							$ 2,491							2,885,946								(3,062,059)
Beginning Balance (in shares) at Mar. 31, 2021								249,073,000
Net issuance of common stock associated with stock options and restricted stock units	(545)							$ 5							(550)
Net issuance of common stock associated with stock options and restricted stock units (in shares)								520,000
Stock-based compensation expense	3,926														3,926
Premium on Mann Group convertible note	22,107														22,107
Issuance of common stock from market price stock purchase	106														106
Issuance of common stock under Market Price Stock Purchase Plan (in shares)								25,000
Net loss	(35,523)																						(35,523)
Ending Balance at Jun. 30, 2021	$ (183,551)							$ 2,496							$ 2,911,535								$ (3,097,582)
Ending Balance (in shares) at Jun. 30, 2021								249,618,000