NEW YORK—Martha Stewart is back at the helm of her namesake company, Martha Stewart Living Omnimedia Inc., the media, lifestyle, and merchandising company she founded. Stewart was elected nonexecutive chairman of the board, the New York-based company announced on Wednesday. She rejoined the board last September at the end of a five-year ban from serving on a board of public companies, as agreed upon with federal regulators after her insider trading trial. Stewart had been chairman of the company from 1996 to 2003. She resigned in 2003 after she was charged with insider trading related to her share sale of biotech company ImClone, a day before the U.S. Food and Drug Administration's decision on an ImClone drug. She was convicted in 2004 and served five months in prison. In a settlement with the Securities and Exchange Commission in 2006 related to a separate civil suit, Stewart agreed to pay a sum of money as well as refrain from serving on the board of any public company for five years.