Stelling began his career with Synovus in March 2006 when the company purchased Riverside Bancshares, Inc., and merged it with Bank of North Georgia, headquartered in Alpharetta, Georgia. Stelling was named President and COO of the combined banks. In June 2008, he was promoted to Synovus Regional CEO for the Atlanta market. Stelling was named Synovus President and Chief Operating Officer in February 2010, acting Chief Executive Officer in June 2010, and President and Chief Executive Officer in October 2010. He became Chairman of the Board in January 2012.

Stelling is a member of the Boards of Directors of the Federal Reserve Bank of Atlanta, Georgia Historical Society, Georgia Power, and the Georgia Chamber of Commerce, which he served as Chairman in 2018. He has also served as a Member of the Board of Regents of the University System of Georgia since 2008 and served as Chairman in 2016.

Stelling is a graduate of the University of Georgia and the Graduate School of Banking of the South, Louisiana State University.

As Chairman and CEO of Synovus, a $45 billion asset bank, Stelling leads a talented team of bankers, investment professionals, and support teams in developing strategies designed to drive growth. Stelling guides a team consisting of commercial, retail, corporate, and financial management services professionals in building long-term relationships while also ensuring the company remains focused on fostering a great working environment, effectively managing risk, reducing expenses, and increasing shareholder value.