Alan Greenspan, who served as chairman of the Federal Reserve for nearly two decades and became one of the most influential central bankers in modern history, has died, the Federal Reserve’s Board of Governors announced on June 22.

The Fed said it noted “with deep sadness” the passing of Greenspan, though no details were immediately provided regarding his age at death or the cause.

Greenspan led the Federal Reserve from 1987 to 2006, a tenure spanning four presidencies. He presided over a prolonged period of economic expansion in the United States during the 1990s and became a towering figure in global financial policymaking, known for his carefully calibrated — and often deliberately opaque — public statements on monetary policy.

His time at the Fed was not without controversy. Critics, particularly following the 2008 financial crisis, argued that his longstanding support for financial deregulation and his reluctance to use monetary policy to deflate asset bubbles contributed to the conditions that precipitated the crisis. Greenspan himself acknowledged in congressional testimony in 2008 that he had found a “flaw” in his ideology, conceding that he had overestimated the ability of financial institutions to self-regulate.

Before his appointment to the Fed by President Ronald Reagan, Greenspan had served as chairman of the Council of Economic Advisers under President Gerald Ford. He was reappointed as Fed chair by Presidents George H.W. Bush, Bill Clinton, and George W. Bush.

Born in New York City in 1926, Greenspan studied economics at New York University and was a long-time associate of the philosopher Ayn Rand before building a career as an economic consultant and policy adviser.

The Board of Governors did not release further details in its initial announcement. A fuller statement was expected from the Fed.