Kenneth Chenault is stepping down after nearly 17 years at the helm of American Express. Warren Buffett called Chenault “the gold standard for corporate leadership.”

Kenneth Chenault, the chairman and CEO of American Express, is stepping down after 37 years at the company, it announced in a press release on Wednesday.

He will be replaced on February 1 by Stephen Squeri, who has been the company’s vice chairman since 2015. Before that, Squeri was the group president of American Express’ Global Corporate Services Group.

“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 has been at the helm of the firm for nearly 17 years, during which American Express’ stock has returned more than 91%, excluding dividends.

Warren Buffett's Berkshire Hathaway is the largest shareholder in American Express, holding 17.15% of 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.