Walmart chief executive Doug McMillon will retire from his post in January, handing over the reins to a longtime deputy. The 59-year-old is stepping down after more than a decade at the helm of America's largest retailer, a period when it successfully expanded its online operations, while scaling back riskier international units. He will be succeeded by John Furner, a Walmart lifer who worked his way up from the shop floor and now serves as head of the company's US business. The change comes as