Dec 16 (Reuters) - Humana (HUM) said on Tuesday that George Renaudin will step down as president of its insurance segment and named Amazon ​healthcare (AMZN) executive Aaron Martin as his successor. Renaudin, who played a pivotal ‌role in establishing and growing the Medicare Advantage and Medicaid programs, will retire next year after ‌a 29-year career at the company, the U.S. health insurer said. Martin was vice president of healthcare at Amazon, where he oversaw strategic partnerships, marketing and ...