Jack Welch, the former CEO of General Electric, has died at age 84.

His death was announced on Monday by his wife, Suzy. The cause of death was renal failure, she told The New York Times.

During Welch's legendary tenure at GE, its value rocketed to $410 billion from $14 billion.

He helmed the company for two decades, then started a business school and became known for his commentary on management issues.

Welch began working for GE in 1960 as a chemical engineer. By 1972 he was a vice president, and by 1979 he was the chairman.

In 1981 he took on the additional role of CEO, which he held until he retired in September 2001.

In his 20 years as CEO, Welch transformed GE into one of the world's most admired and successful companies with his innovative management techniques.

Revenue grew fivefold, to $130 billion from about $25 billion, while income grew tenfold, to $15 billion from $1.5 billion, and the company's market capitalization increased thirtyfold, to about $410 billion.

His achievements are considered epic, and companies around the world have adopted the "Welch way."

In 2010 Welch founded the Jack Welch Management Institute, a business school that offers executive education and management training.

"He became the gold standard of greatness, the icon of industrial imagination," Jeffrey Sonnenfeld, a Yale University business professor who had known Welch since the 1980s, told Bloomberg. "His track record over those 20 years as CEO is hard to see excelled anywhere."

President Donald Trump tweeted about Welch on Monday following the news of his death.