Note 10 - Net Loss Per Share - Anti-dilutive Securities (Details) - shares shares in Thousands		3 Months Ended		9 Months Ended
		Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021
Potentially dilutive common shares (in shares)		50,865	50,518	48,792	45,323
Unvested Stock [Member]
Potentially dilutive common shares (in shares)		1,918	1,831	1,751	1,581
Convertible Preferred Stocks [Member]
Potentially dilutive common shares (in shares)		47,707	34,095	45,653	29,174
Common Stock Warrants [Member]
Potentially dilutive common shares (in shares)		1,240	2,510	1,388	2,486
IPO Warrants [Member]
Potentially dilutive common shares (in shares)	[1]	0	12,082	0	12,082

[1] The IPO Warrants were issued in connection with our initial public offering in 2015. The IPO Warrants are exercisable at a price of $11.50 per share and expire on July 24, 2022. The Company may redeem the IPO Warrants at a price of $0.01 per IPO Warrant upon 30 days’ notice only if the last sale price of our common stock is at least $17.50 per share for any 20 trading days within a 30 trading day period. If the Company redeems the IPO Warrants in this manner, the Company will have the option to do so on a cashless basis with the issuance of an economically equivalent number of shares of Company common stock.