Carlyle Group, which owns an 18-percent stake in Butterfield bank, plans to float on the US stock market.The private-equity firm’s current owners, including the three founders, plan to keep their stakes when Carlyle holds its initial public offering, according to a person familiar with the plans.William Conway, Daniel D’Aniello and David Rubenstein won’t sell any of the shares in the firm they founded in 1987, said the person, who asked not to be identified because the information is private. Other owners, including partners, the California Public Employees Retirement System, and Mubadala Development Co, an investment company controlled by Abu Dhabi, also plan to keep their stakes, the person said.Randall Whitestone, a spokesman for Washington-based Carlyle, declined to comment on the plans.As a publicly traded company, Carlyle would need be required to provide more information about their investments, including that in Butterfield.Carlyle invested $150 million in Butterfield two years in return for new equity priced at $1.21 per share. At the same time, the Canadian Imperial Bank of Commerce (CIBC) also invested $150 million.The liquidity injection helped Butterfield to stabilise and de-risk its balance sheet after years of heavy losses owing to soured investments linked to the US housing market.Butterfield’s share price closed at $1.10 yesterday on the Bermuda Stock Exchange.Carlyle joins New York-based rivals Blackstone Group LP and KKR & Co in seeking to become a publicly traded company.Carlyle, which has contemplated an IPO since at least 2007, signalled in a filing with the US Securities and Exchange Commission this month that it may sell a 10 percent stake in the IPO, saying existing owners would retain 90 percent of a Carlyle holding entity. Carlyle said it intends to use the proceeds of the offering to repay debt as well as for acquisitions and strategic investments.Carlyle’s owners paid themselves a $398.5 million dividend in December 2010, nine months before the firm filed to go public, by borrowing $500 million from Mubadala. Carlyle repaid the remaining balance to Mubadala last month, refinancing it with new debt, according to a regulatory filing.The firm’s three founders earned a combined $413 million last year, mainly from distributions.