Idaho Code § 67-423A
If in the event a legislator dies or resigns the office, the legislator's emergency interim successor highest in order of succession who is not unavailable shall, except for the power and duty to appoint emergency successors, exercise the powers and assume the duties of such legislator. An emergency interim successor shall exercise these powers and assume these duties until an emergency interim successor higher in order of succession, or a replacement legislator appointed pursuant to section 59-904A, Idaho Code, and legally qualified can act. Each house of the legislature shall, in accordance with its own rules, determine who is entitled under the provisions of this chapter to exercise the powers and assume the duties of its members. All constitutional and statutory provisions pertaining to ouster of a legislator shall be applicable to an emergency interim successor who is exercising the powers and assuming the duties of a legislator.
Idaho Code § 67-423A