A $10,000 investment in this utility company 15 years ago would be worth $51,883 today.There's a saying on Wall Street: "Boring is beautiful." Sure enough, there's nothing glamorous about America's largest water utility, but its long-term shareholders aren't complaining. Over the last 15 years, shares of American Water Works (AWK +0.19%) have delivered an average annualized return of 11.6% that turned every $10,000 invested into $51,883. With dividends reinvested, that amount would have snowballed into $72, ...