Kenneth Lewis, the CEO and president of one of the nation’s leading banks, announced Wednesday that he will retire at the end of the year, after 40 years of service. Bank of America’s board has not named Lewis’ successor, but said a new chief would be appointed by December 31. “Bank of America is well positioned to meet the continuing challenges of the economy and markets,” Lewis said. “I am particularly heartened by the results that are emerging from the decisions and initiatives of the difficult past year-and-a-half.”

Lewis noted in a written statement that the bank’s Merrill Lynch and Countrywide integrations are on track and yielding value, and that Bank of America was now in a position to begin repaying the federal government’s TARP money. “For these reasons, I decided now is the time to begin to transition to the next generation of leadership at Bank of America,” Lewis said. But all of the major mainstream media outlets were abuzz Thursday with speculation of Lewis’ abrupt departure. The Wall Street Journal said “a person close to him says Mr. Lewis was fed up with the criticism that haunted him following the takeover of Merrill Lynch.” The New York Times said B of A’s takeover of Merrill was Lewis’ downfall, adding that the bank’s board appeared caught off-guard by the timing of his announcement, though no one asked Lewis to stay. American Banker said that in addition to facing numerous legal challenges over Merrill, Bank of America and Lewis were fighting against high losses from several loan portfolios. Reports say that federal authorities didn’t press Lewis to resign, although the administration’s tightened scrutiny and partial stake in the bank will likely give it some pull in the decision of who will take the reins at Bank of America next.