General Re, a unit of Warren Buffett’s Berkshire Hathaway Inc., promoted Bill Rotatori to chief executive officer of its asset management unit that oversees $63 billion for clients including insurers.

Rotatori replaces Jerry Lynch, who will retire on Dec. 31, Stamford, Connecticut-based General Re said today in a statement. Chip Clark was appointed president, filling Rotatori’s previous role.

Lynch founded New England Asset Management in 1984 and sold it in 1995 to General Re, a global reinsurer. Buffett bought General Re in 1998 for $17.7 billion in what was then his largest takeover. Unaffiliated assets under management climbed from $9.4 billion since 1995 while the unit’s number of insurance clients more than doubled to 100, according to the statement.

“Jerry and his team’s combination of investment acumen, a superb technology platform and efficient investment accounting services has driven their success,” General Re CEO Tad Montross said in the statement. “I am very pleased with the transition to Bill and Chip.”

BlackRock Inc., Goldman Sachs Group Inc. and JPMorgan Chase & Co. are among asset managers vying to oversee funds for insurers. Underwriters coping with low interest rates and increased regulation have increasingly been turning to third- party money managers.

Lynch will be non-executive chairman of GR-NEAM after his retirement, according to the statement.