Okla. Stat. tit. 36, § 1620

A. An insurer may invest or deposit any of its cash funds on deposit in checking or savings accounts, under certificates of deposit, or in solvent banks or trust companies, which are insured by the Federal Deposit Insurance Corporation. B. An insurer may invest or deposit any of its funds in checking, share or saving accounts under certificates of deposit or time deposits in solvent savings and loan associations which are insured by the Federal Deposit Insurance Corporation. C. An insurer may invest or deposit any of its cash funds in share, share draft, under certificates of deposit or time deposits in solvent credit unions which are insured by the National Credit Union Administration. D. All certificates of deposits or other time deposit instruments shall be classified as negotiable and transferrable as required by Section 1703 of this title.