CONSOLIDATED STATEMENTS OF SHAREHOLDERS' EQUITY - USD ($) shares in Thousands, $ in Thousands	Common Stock	Additional Paid-In Capital	Accumulated Deficit	Total
Balance at Dec. 31, 2021	$ 2,204	$ 1,794,525	$ (1,471,143)	$ 325,586
Balance (in shares) at Dec. 31, 2021	220,361
Increase (Decrease) in Shareholders' Equity (Deficit)
Net loss			(24,145)	(24,145)
Issuance of common stock pursuant to the exercise of stock options and employee stock purchase plan	$ 1	619		620
Issuance of common stock pursuant to the exercise of stock options and employee stock purchase plan (in shares)	173
Restricted stock units vested (in shares)	2
Stock option and restricted stock compensation expense		4,196		4,196
Directors' deferred share unit compensation		211		211
Balance at Mar. 31, 2022	$ 2,205	1,799,551	(1,495,288)	306,468
Balance (in shares) at Mar. 31, 2022	220,536
Increase (Decrease) in Shareholders' Equity (Deficit)
Net loss			(62,021)	(62,021)
Issuance of common stock pursuant to the exercise of stock options and employee stock purchase plan	$ 1	410		411
Issuance of common stock pursuant to the exercise of stock options and employee stock purchase plan (in shares)	108
Stock option and restricted stock compensation expense		4,760		4,760
Directors' deferred share unit compensation		213		213
Balance at Jun. 30, 2022	$ 2,206	1,804,934	(1,557,309)	249,831
Balance (in shares) at Jun. 30, 2022	220,644
Increase (Decrease) in Shareholders' Equity (Deficit)
Net loss			(77,755)	(77,755)
Issuance of common stock pursuant to the exercise of stock options and employee stock purchase plan	$ 2	447		449
Issuance of common stock pursuant to the exercise of stock options and employee stock purchase plan (in shares)	107
Stock option and restricted stock compensation expense		5,336		5,336
Directors' deferred share unit compensation		146		146
Balance at Sep. 30, 2022	$ 2,208	1,810,863	(1,635,064)	178,007
Balance (in shares) at Sep. 30, 2022	220,751
Increase (Decrease) in Shareholders' Equity (Deficit)
Net loss			(59,008)	(59,008)
Issuance of common stock pursuant to the exercise of stock options and employee stock purchase plan	$ 1	423		424
Issuance of common stock pursuant to the exercise of stock options and employee stock purchase plan (in shares)	103
Issuance of common stock, net of issuance costs	$ 51	25,596		25,647
Issuance of common stock, net of issuance costs (in shares)	5,167
Restricted stock units vested (in shares)	25
Stock option and restricted stock compensation expense		10,610		10,610
Directors' deferred share unit compensation		146		146
Balance at Dec. 31, 2022	$ 2,260	1,847,638	(1,694,072)	$ 155,826
Balance (in shares) at Dec. 31, 2022	226,046			226,046
Increase (Decrease) in Shareholders' Equity (Deficit)
Net loss			(41,014)	$ (41,014)
Issuance of common stock pursuant to the exercise of stock options and employee stock purchase plan	$ 1	38		39
Issuance of common stock pursuant to the exercise of stock options and employee stock purchase plan (in shares)	16
Stock option and restricted stock compensation expense		6,916		6,916
Directors' deferred share unit compensation	$ 8	151		151
Balance at Mar. 31, 2023	$ 2,261	$ 1,854,743	$ (1,735,086)	$ 121,918
Balance (in shares) at Mar. 31, 2023	226,070			226,070