Consolidated Statements of Stockholders' Equity - USD ($) shares in Thousands, $ in Thousands	Total	Cumulative Effect, Period of Adoption, Adjustment	Common Stock	Additional Paid-in Capital	Accumulated Other Comprehensive Income (Loss)	Accumulated Deficit	Accumulated Deficit Cumulative Effect, Period of Adoption, Adjustment
Beginning balance (in shares) at Dec. 31, 2018			49,338
Beginning balance at Dec. 31, 2018	$ 72,116		$ 49	$ 631,605	$ (687)	$ (558,851)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock on bond conversion (in shares)			19,460
Issuance of common stock on bond conversion	133,299		$ 19	133,280
Issuance of restricted stock, net of shares withheld for taxes, and other (in shares)			666
Issuance of restricted stock, net of shares withheld for taxes, and other	(600)		$ 1	(601)
Issuance of common stock under ESPP (in shares)			297
Issuance of common stock under ESPP	$ 1,075		$ 1	1,074
Issuance of common stock from option exercises (in shares)	197		195
Issuance of common stock from option exercises	$ 1,058			1,058
Stock-based compensation expense	11,349			11,349
Net loss	(64,790)					(64,790)
Other comprehensive income (loss), net of taxes	105				105
Ending balance (in shares) at Dec. 31, 2019			69,956
Ending balance at Dec. 31, 2019	$ 153,612	$ (100)	$ 70	777,765	(582)	(623,641)	$ (100)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Accounting Standards Update [Extensible List]	Accounting Standards Update 2016-13 [Member]
Issuance of common stock from at-the-market offering, net of commissions (in shares)			2,480
Issuance of common stock from at-the-market offering, net of commissions	$ 20,226		$ 2	20,224
Issuance of restricted stock, net of shares withheld for taxes, and other (in shares)			1,050
Issuance of restricted stock, net of shares withheld for taxes, and other	(459)		$ 1	(460)
Issuance of common stock under ESPP (in shares)			476
Issuance of common stock under ESPP	$ 1,323		$ 1	1,322
Issuance of common stock from option exercises (in shares)	100		96
Issuance of common stock from option exercises	$ 451			451
Equity issuance costs	(176)			(176)
Stock-based compensation expense	14,450			14,450
Acquisition of InstruNor AS (in shares)			485
Acquisition of InstruNor AS	2,049		$ 1	2,048
Net loss	(53,020)					(53,020)
Other comprehensive income (loss), net of taxes	$ 694				694
Ending balance (in shares) at Dec. 31, 2020	74,543		74,543
Ending balance at Dec. 31, 2020	$ 139,050		$ 75	815,624	112	(676,761)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of restricted stock, net of shares withheld for taxes, and other (in shares)			2,047
Issuance of restricted stock, net of shares withheld for taxes, and other	(1,793)		$ 2	(1,795)
Issuance of common stock under ESPP (in shares)			292
Issuance of common stock under ESPP	$ 1,285			1,285
Issuance of common stock from option exercises (in shares)	37		37
Issuance of common stock from option exercises	$ 209			209
Stock-based compensation expense	16,101			16,101
Net loss	(59,237)					(59,237)
Other comprehensive income (loss), net of taxes	$ (1,019)				(1,019)
Ending balance (in shares) at Dec. 31, 2021	76,919		76,919
Ending balance at Dec. 31, 2021	$ 94,596		$ 77	$ 831,424	$ (907)	$ (735,998)