American Express' CEO is stepping down

American Express Chairman and Chief Executive Officer Kenneth Chenault is stepping down after 37 years at the company, a company press release said on Wednesday.

He will be replaced by Stephen Squeri, who has served as the company's vice chairman since 2015. Before that, Squeri was the group president of American Express' Global Corporate Services Group. Sequeri will assume the roles of chairman and CEO as of February 1, 2018.

"We are completing a two-year turnaround ahead of plan with strong revenue and earnings growth across all of our business segments," Chenault said in the press release. "We've added new products and benefits, acquired record numbers of new customers, expanded our merchant network and lowered operating costs. We've dealt effectively with competitive challenges and redesigned our marketing, customer service and risk management capabilities for the digital age."

Chenault's departure comes after serving at the helm of the firm for nearly 17 years, during which American Express' stock returned more than 91%, excluding dividends.

Warren Buffett's Berkshire Hathaway is the largest shareholder in American Express, holding 17.15% of the outstanding shares, according to Bloomberg.

"Ken's been the gold standard for corporate leadership and the benchmark that I measure others against," Buffett said in the release. "He led the company through 9/11, the financial crisis and the challenges of the last couple of years. American Express always came out stronger."

"He's been a great CEO and Berkshire Hathaway shareholders owe him a huge thank you," Buffett concluded.