Former Microsoft CEO Steve Ballmer is leaving the company’s board, he said in a letter posted on the company’s website Tuesday morning. “Given my confidence and the multitude of new commitments I am taking on now, I think it would be impractical for me to continue to serve on the board, and it is best for me to move off,” he wrote to CEO Satya Nadella. Ballmer served as the second CEO of the Redmond-based tech giant for about a decade.