When two or more insured banks merge, the deposits from the assumed bank continue to be insured separately for at least six months after the merger. This grace period gives a depositor the opportunity to restructure his or her accounts, if necessary.
CDs from the assumed bank are separately insured until the earliest maturity date after the end of the six-month grace period. CDs that mature during the six-month period and are renewed for the same term and in the same dollar amount (either with or without accrued interest) continue to be separately insured until the first maturity date after the six-month period. If a CD matures during the six-month grace period and is renewed on any other basis, it would be separately insured only until the end of the six-month grace period.
More information about FDIC insurance can be found at http://www.fdic.gov/deposit/deposits/insured/faq2.html