(Reuters) - Visa Inc said on Monday that Chief Executive Charles Scharf, who orchestrated the company's reunion with its European affiliate, would step down on Dec. 1. Visa's shares, which have more than tripled in value under Scharf's watch, were down 1.8 percent at $80.70 in after-market trading. San Francisco-based company named Alfred Kelly, a former president of American Express Co and a current Visa board member, as CEO.