Note 10 - Net Loss Per Share - Anti-dilutive Securities (Details) - shares shares in Thousands		3 Months Ended
		Mar. 31, 2020	Mar. 31, 2019
Potentially dilutive common shares (in shares)		31,111	25,075
Unvested Stock [Member]
Potentially dilutive common shares (in shares)	[1]	1,160	490
Convertible Preferred Stocks [Member]
Potentially dilutive common shares (in shares)		15,905	11,127
Common Stock Warrants [Member]
Potentially dilutive common shares (in shares)		1,964	1,376
IPO Warrants [Member]
Potentially dilutive common shares (in shares)	[2]	12,082	12,082

[1] Does not include [$ ] million shares and 10.8 million shares for the three months ended March 31, 2020 and 2019, respectively, of unvested stock because the performance conditions had not yet been satisfied.

[2] 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.