U.S. Securities and Exchange Commission Enforcement Division head Robert Khuzami is leaving the agency after a nearly four-year tenure that included a massive restructuring and record number of new cases.

Khuzami, who has not announced his future plans, joined the SEC when the agency was at a low point, reeling from its failure to detect Bernard Madoff’s Ponzi scheme. He moved swiftly to transform the 1,100-person Enforcement Division, overseeing a top-to-bottom overhaul of how the agency detects and prosecutes wrongdoing in the financial marketplace.