. the company accounts for share repurchases retired after repurchase by allocating the excess repurchase price over par to additional paid- in-capital . other common stock activity other common stock activity includes shares withheld to pay taxes for share-based compensation , exercises of stock options , and other activity . during the year ended december a031 , 2017 , it also includes a $ 3 million conversion of the company's convertible debentures into 0.3 million shares of common stock