Butterfield Bank spent $1.84 million buying back nearly 1.5 million of its own shares in September.In a filing with the Bermuda Stock Exchange (BSX) yesterday, the bank said it bought for Treasury 1,494,678 common shares at an average cost of 1.232 per share.By repurchasing their own shares, companies effectively increase the book value of the remaining shares outstanding. It is regarded as a way of returning capital to shareholders.Butterfield Bank has more than 557 million common shares outstanding, acording to BSX data.