v3.19.3
Condensed Consolidated Balance Sheets (Current Period Unaudited) (Parentheticals) - USD ($)
Sep. 30, 2019
Dec. 31, 2018
Dec. 31, 2017
Preferred stock, par value (in dollars per share) $ 0.001 $ 0.001  
Preferred stock, shares authorized (in shares) 1,000,000 1,000,000  
Preferred stock, shares issued (in shares) 0 0  
Preferred stock, shares outstanding (in shares) 0 0  
Common stock, par value (in dollars per share) $ 0.001 $ 0.001 $ 0.001
Common stock, shares authorized (in shares) 95,000,000 5,313,200 148,000,000
Common stock, shares issued (in shares) 5,807,877 701,808 19,548,969
Common stock, shares outstanding (in shares) 5,807,877 701,808 19,548,969
Series A Redeemable Convertible Preferred Stock Without Giving Effect To The Reverse Stock Split [Member]      
Redeemable convertible preferred stock, par value $ 0.001 $ 0.001 $ 0.001
Redeemable convertible preferred stock, shares authorized (in shares) 0 2,046,378 57,002,183
Redeemable convertible preferred stock, shares issued (in shares) 0 2,034,548 56,672,658
Redeemable convertible preferred stock, shares outstanding (in shares) 0 2,034,548 56,672,658
Redeemable convertible preferred stock, liquidation value     $ 12,898,697,000
Series B Redeemable Convertible Preferred Stock Without Giving Effect To The Reverse Stock Split [Member]      
Redeemable convertible preferred stock, par value $ 0.001 $ 0.001 $ 0.001
Redeemable convertible preferred stock, shares authorized (in shares) 0 1,833,387 51,069,262
Redeemable convertible preferred stock, shares issued (in shares) 0 1,833,387 51,069,262
Redeemable convertible preferred stock, shares outstanding (in shares) 0 1,833,387 51,069,262
Redeemable convertible preferred stock, liquidation value     $ 16,000,000,000