Consolidated Statements of Stockholders' Equity (Deficit) (Unaudited) - USD ($) $ in Thousands	Common Stock [Member]	Additional Paid-in Capital [Member]	AOCI Attributable to Parent [Member]	Retained Earnings [Member]	Total
Balance at Dec. 31, 2019	$ 1,541	$ 877,300	$ 39	$ (840,628)	$ 38,252
Net loss				(37,599)	(37,599)
Other comprehensive income (loss)	0	0	(25)	0	(25)
Exercise of stock options, net	1	265			266
Stock-based compensation expense		2,754			2,754
Balance at Mar. 31, 2020	1,542	880,319	14	(878,227)	3,648
Balance at Dec. 31, 2020	1,769	1,002,408	3	(1,023,442)	(19,262)
Net loss				(64,284)	(64,284)
Other comprehensive income (loss)			179		179
Employee stock purchase plan sales, net	2	721			723
Exercise of stock options, net	6	2,171	0	0	2,177
Stock-based compensation expense		5,479			5,479
Balance at Mar. 31, 2021	$ 1,777	$ 1,010,779	$ 182	$ (1,087,726)	$ (74,988)