Consolidated Statements of Stockholders' Deficit Parentheticals - shares	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Exercise of stock options, net (in shares)	1,276,000
Employee stock purchase plan sales, net (in shares)	338,000	260,000	321,000
Issuance of common stock, net (in shares)			3,846,000
Warrants exercised (in shares)	14,997,000	253,000
Shares withheld for taxes for vesting of restricted stock units (in shares)	59,000
Common Stock
Exercise of stock options, net (in shares)		2,573,000	3,290,000
Employee stock purchase plan sales, net (in shares)	338,000	260,000	321,000
Issuance of shares to directors in lieu of cash retainer (in shares)	37,000	32,000	9,000
Common Stock | Restricted Stock Units (RSUs)
Stock option awards vested (in shares)	1,276,000	439,000