Consolidated Statements of Stockholders' Equity - USD ($) $ in Thousands	Common Stock [Member]	Treasury Stock [Member]	Additional Paid-In Capital [Member]	Accumulated Other Comprehensive Loss [Member]	Accumulated Deficit [Member]	Total
Beginning Balance at Dec. 31, 2019	$ 548	$ (53)	$ 489,925	$ 20	$ (183,143)	$ 307,297
Beginning Balance (in shares) at Dec. 31, 2019	54,773,061
Issuance of common stock pursuant to exercise of stock options	$ 3	0	(3)	0	0	0
Issuance of common stock pursuant to exercise of stock options (in shares)	386,974
Share repurchase	$ 0	0	(72)	0	0	(72)
Share repurchase (in shares)	(3,000)
Sale of treasury stock	$ 0	53	0	0	0	53
Sale of treasury stock (in shares)	0
Issuance of treasury stock pursuant to exercise of stock options	$ 0	(429)	0	0	0	(429)
Issuance of treasury stock pursuant to exercise of stock options (in shares)	0
Unrealized comprehensive gain (loss) on investments	$ 0	0	0	(95)	0	(95)
Share-based compensation	0	0	3,961	0	0	3,961
Net loss	0	0	0	0	(24,664)	(24,664)
Ending Balance at Mar. 31, 2020	$ 551	(429)	493,811	(75)	(207,807)	286,051
Ending Balance (in shares) at Mar. 31, 2020	55,157,035
Beginning Balance at Dec. 31, 2019	$ 548	(53)	489,925	20	(183,143)	307,297
Beginning Balance (in shares) at Dec. 31, 2019	54,773,061
Unrealized comprehensive gain (loss) on investments						209
Net loss						(49,704)
Ending Balance at Jun. 30, 2020	$ 551	0	498,590	229	(232,847)	266,523
Ending Balance (in shares) at Jun. 30, 2020	55,170,003
Beginning Balance at Mar. 31, 2020	$ 551	(429)	493,811	(75)	(207,807)	286,051
Beginning Balance (in shares) at Mar. 31, 2020	55,157,035
Issuance of common stock pursuant to exercise of stock options	$ 0	0	290	0	0	290
Issuance of common stock pursuant to exercise of stock options (in shares)	12,968
Sale of treasury stock	$ 0	538	0	0	0	538
Sale of treasury stock (in shares)	0
Issuance of treasury stock pursuant to exercise of stock options	$ 0	(109)	0	0	0	(109)
Issuance of treasury stock pursuant to exercise of stock options (in shares)	0
Unrealized comprehensive gain (loss) on investments	$ 0	0	0	304	0	304
Share-based compensation	0	0	4,489	0	0	4,489
Net loss	0	0	0	0	(25,040)	(25,040)
Ending Balance at Jun. 30, 2020	$ 551	0	498,590	229	(232,847)	266,523
Ending Balance (in shares) at Jun. 30, 2020	55,170,003
Beginning Balance at Dec. 31, 2020	$ 610	0	825,794	(42)	(322,843)	503,519
Beginning Balance (in shares) at Dec. 31, 2020	60,996,367
Issuance of common stock pursuant to exercise of stock options	$ 9	0	8,783	0	0	8,792
Issuance of common stock pursuant to exercise of stock options (in shares)	991,432
Unrealized comprehensive gain (loss) on investments	$ 0	0	0	(33)	0	(33)
Share-based compensation	0	0	7,900	0	0	7,900
Net loss	0	0	0	0	(40,179)	(40,179)
Ending Balance at Mar. 31, 2021	$ 619	0	842,477	(75)	(363,022)	479,999
Ending Balance (in shares) at Mar. 31, 2021	61,987,799
Beginning Balance at Dec. 31, 2020	$ 610	0	825,794	(42)	(322,843)	503,519
Beginning Balance (in shares) at Dec. 31, 2020	60,996,367
Unrealized comprehensive gain (loss) on investments						(39)
Net loss						(74,704)
Ending Balance at Jun. 30, 2021	$ 634	0	886,431	(81)	(397,547)	489,437
Ending Balance (in shares) at Jun. 30, 2021	63,448,069
Beginning Balance at Mar. 31, 2021	$ 619	0	842,477	(75)	(363,022)	479,999
Beginning Balance (in shares) at Mar. 31, 2021	61,987,799
Issuance of common stock pursuant to exercise of stock options	$ 2	0	1,113	0	0	1,115
Issuance of common stock pursuant to exercise of stock options (in shares)	133,838
Conversion of convertible securities into common shares	$ 13	0	35,530	0	0	35,543
Conversion of convertible securities into common shares (in shares)	1,326,432
Unrealized comprehensive gain (loss) on investments	$ 0	0	0	(6)	0	(6)
Share-based compensation	0	0	7,311	0	0	7,311
Net loss	0	0	0	0	(34,525)	(34,525)
Ending Balance at Jun. 30, 2021	$ 634	$ 0	$ 886,431	$ (81)	$ (397,547)	$ 489,437
Ending Balance (in shares) at Jun. 30, 2021	63,448,069