This excerpt taken from the C 10-Q filed May 4, 2007.
Fair Value Option for Financial Assets and Financial Liabilities (SFAS 159)
On February 15, 2007, the FASB issued SFAS No. 159, "The Fair Value Option for Financial Assets and Financial Liabilities" (SFAS 159 or fair value option accounting). Under SFAS 159, the Company may elect to report most financial instruments and certain other items at fair value on an instrument-by-instrument basis with changes in fair value reported in earnings. After the initial adoption, the election is made at the acquisition of an eligible financial asset, financial liability, or firm commitment or when certain specified reconsideration events occur. The fair value election may not be revoked once an election is made.
Additionally, the transition provisions of SFAS 159 permit a one-time election for existing positions at the adoption date with a cumulative-effect adjustment included in opening retained earnings and future changes in fair value reported in earnings.