Note 10 - Net Loss Per Share Attributable to Common Stockholders - Anti-dilutive Securities (Details) - shares shares in Thousands		12 Months Ended
		Dec. 31, 2019	Dec. 31, 2018
Potentially dilutive common shares (in shares)		28,302	16,586
Unvested Stock [Member]
Potentially dilutive common shares (in shares)	[1]	861	498
Convertible Preferred Stocks [Member]
Potentially dilutive common shares (in shares)		13,697	3,552
Common Stock Warrants [Member]
Potentially dilutive common shares (in shares)		1,662	454
IPO Warrants [Member]
Potentially dilutive common shares (in shares)	[2]	12,082	12,082

[1] Does not include 3.6 million shares and 10.8 million shares of unvested stock for the year ended December 31, 2019 and 2018 because the performance conditions had not yet been satisfied as of December 31, 2019 and 2018, respectively.

[2] The IPO Warrants are exercisable at a price of $11.50 per share and expire July 24, 2022. The Company may redeem the 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.