Note 5 - Common Stock	9 Months Ended
Sep. 30, 2020
Notes to Financial Statements
Stockholders' Equity Note Disclosure [Text Block]	5. Common Stock Pursuant to its Articles, the Company has an unlimited number of shares available for issuance with no par value. During June 2019, under the Common Shares Purchase Agreement with Piper Jaffray & Co., the Company sold 4.8 million shares of common stock at a price $8.25 per share for total net proceeds of $37.5 million, including the capitalized underwriter’s commission of $2.3 million and other related fees of $0.2 million. From January through December 2019, 771 thousand shares of common stock were issued upon the exercise of stock options at a price of $2.50 to $15.00 per share for total proceeds of $3.8 million. On January 4, 2020, XBiotech announced that it had commenced a “modified Dutch auction” tender offer to purchase up to $420.0 million of its common shares, or such lesser number of common shares as are properly tendered and not properly withdrawn, at a price not less than $30.00 nor greater than $33.00 per common share, to the seller in cash. The tender offer expired on February 12, 2020. On February 19, 2020, the Company announced the final results of its “modified Dutch Auction” tender offer. The Company accepted for purchase 14,000,000 shares of its common stock, $0.01 par value per share, at a price of $30 per share, for an aggregate cost of approximately $420.0 million, excluding fees and expenses related to the tender offer. These shares represented approximately 32.67 percent of the shares outstanding. $6.66 per share or total of $93.24 million of these share repurchases have been classified to reduce common stock and $23.34 per share or total of $326.76 million of these share repurchases have been classified to reduce retained earnings in the accompanying consolidated balance sheet as of September 30, 2020. From January through September 2020, 1.7 million shares of common stock were issued upon the exercise of stock options at a price of $2.71 to $19.09 per share for total proceeds of $10.4 million.

Note 5 - Common Stock

9 Months Ended

Sep. 30, 2020

Stockholders' Equity Note Disclosure [Text Block]

5. Common Stock

Pursuant to its Articles, the Company has an unlimited number of shares available for issuance with no par value.

During June 2019, under the Common Shares Purchase Agreement with Piper Jaffray & Co., the Company sold 4.8 million shares of common stock at a price $8.25 per share for total net proceeds of $37.5 million, including the capitalized underwriter’s commission of $2.3 million and other related fees of $0.2 million.

From January through December 2019, 771 thousand shares of common stock were issued upon the exercise of stock options at a price of $2.50 to $15.00 per share for total proceeds of $3.8 million.

On January 4, 2020, XBiotech announced that it had commenced a “modified Dutch auction” tender offer to purchase up to $420.0 million of its common shares, or such lesser number of common shares as are properly tendered and not properly withdrawn, at a price not less than $30.00 nor greater than $33.00 per common share, to the seller in cash. The tender offer expired on February 12, 2020.

On February 19, 2020, the Company announced the final results of its “modified Dutch Auction” tender offer. The Company accepted for purchase 14,000,000 shares of its common stock, $0.01 par value per share, at a price of $30 per share, for an aggregate cost of approximately $420.0 million, excluding fees and expenses related to the tender offer. These shares represented approximately 32.67 percent of the shares outstanding. $6.66 per share or total of $93.24 million of these share repurchases have been classified to reduce common stock and $23.34 per share or total of $326.76 million of these share repurchases have been classified to reduce retained earnings in the accompanying consolidated balance sheet as of September 30, 2020.

From January through September 2020, 1.7 million shares of common stock were issued upon the exercise of stock options at a price of $2.71 to $19.09 per share for total proceeds of $10.4 million.