DETROIT – Shares of CarMax Inc. fell more than 10% during premarket trading Thursday after the used car retailer announced the unexpected departure of CEO Bill Nash.The company said board member David McCreight, a retail clothing executive who has served as CEO of Lulu's Fashion Lounge Holdings and president of Urban Outfitters Inc., will serve as CarMax's interim CEO until a permanent replacement has been found.CarMax also said Chair Tom Folliard, an executive with a 30-year history with the company, inclu ...