Idaho Code § 19-1904
A court may direct that one (1) or more jurors in addition to the regular panel be called and impaneled to sit as alternate jurors. All jurors shall be drawn in the same manner, shall have the same qualifications, shall be subject to the same examination and challenges, shall take the same oath, and shall have the same functions, powers, facilities, and privileges prior to deliberations. At the conclusion of closing arguments, jurors exceeding the number required of a regular panel shall be removed by lot. Those removed by lot may be discharged after the jury retires to consider its verdict. If more than one (1) additional juror is called, each party is entitled to two (2) peremptory challenges in addition to those otherwise allowed by law; provided however, that if only one (1) additional juror is called, each party shall be entitled to one (1) peremptory challenge in addition to those otherwise provided by law.
Idaho Code § 19-1904