Note 10 - Net Loss Per Share - Anti-dilutive Securities (Details) - shares shares in Thousands		3 Months Ended		6 Months Ended
		Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
Potentially dilutive common shares (in shares)		57,262	43,639	55,370	31,226
Unvested Stock [Member]
Potentially dilutive common shares (in shares)		1,981	1,555	1,666	1,034
Convertible Preferred Stocks [Member]
Potentially dilutive common shares (in shares)		41,725	27,129	40,159	16,143
Common Stock Warrants [Member]
Potentially dilutive common shares (in shares)		1,474	2,873	1,463	1,967
IPO Warrants [Member]
Potentially dilutive common shares (in shares)	[1]	12,082	12,082	12,082	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.