NOTES TO CONSOLIDATED FINANCIAL STATEMENTS - Continued Unum Group and Subsidiaries Note 10 - Stockholders' Equity and Earnings Per Common Share - Continued Common stock repurchases, which are accounted for using the cost method and classified as treasury stock until otherwise retired, were as follows: Year Ended December 31 2019 2018 2017 (in millions) Shares Repurchased 12.3  8.7  8.2  Cost of Shares Repurchased (1) $ 400.4 $ 350.7 $ 400.4 (1) Includes commissions of $0.4 million, $0.7 million, and $0.3 million for the years ended December 31, 2019, 2018, and 2017, respectively. Unum Group has 25.0 million shares of preferred stock authorized with a par value of $0.10 per share. No preferred stock has been issued to date. Under the Stock Incentive Plan of 2017 (the 2017 Plan), up to 17 million shares of common stock are available for awards to our employees, officers, consultants, and directors. Awards may be in the form of stock options, stock appreciation rights, restricted stock, restricted stock units, performance share units, and other stock-based awards. Each full-value award, defined as any award other than a stock option or stock appreciation right, is counted as 1.76 shares. The exercise price for stock options issued cannot be less than the fair value of the underlying common stock as of the grant date. Stock options generally have a term of eight years after the date of grant and fully vest after three years. At December 31, 2019, approximately 13.9 million shares were available for future grants under the 2017 Plan. Under the Stock Incentive Plan of 2012 (the 2012 Plan), which was terminated in May 2017 for the purposes of any further grants, up to 20 million shares of common stock were available for awards to our employees, officers, consultants, and directors. Awards could be in the form of stock options, stock appreciation rights, restricted stock, restricted stock units, performance share units, and other stock-based awards. Each full-value award, defined as any award other than a stock option or stock appreciation right, is counted as 1.76 shares. Awards granted before the termination of the 2012 Plan remain outstanding in accordance with the plan's terms. Stock options generally have a term of eight years after the date of grant and fully vest after three years.  Under the Stock Incentive Plan of 2007 (the 2007 Plan), which was terminated in May 2012 for purposes of any further grants, up to 35 million shares of common stock were available for awards to our employees, officers, consultants, and directors. Awards could be in the form of stock options, stock appreciation rights, restricted stock, restricted stock units, performance share units, and other stock-based awards. Each full-value award, defined as any award other than a stock option or stock appreciation right, is counted as 2.7 shares. Awards granted before the termination of the 2007 Plan remain outstanding in accordance with the plan's terms. Stock options generally have a term of eight years after the date of grant and fully vest after three years.  We issue new shares of common stock for all of our stock plan vestings and exercises. Preferred Stock Note 11 - Stock-Based Compensation Description of Stock Plans 179