By Angela Moon NEW YORK (Reuters) - Stocks fell on Wednesday with the S&P 500 posting its biggest decline in three weeks, after minutes from the latest U.S. Federal Reserve meeting showed some officials were open to tapering large-scale asset purchases as early as at the June meeting. Trading was volatile - the Dow and the S&P indexes both rose more than 1 percent during the morning, but fell more than 1 percent in the afternoon.