Idaho Code § 15-2-606: Failure of testamentary provision.

(a) Except as provided in section 15-2-605 of this Part, if a devise other than a residuary devise fails for any reason, it becomes a part of the residue.

(b) Except as provided in section 15-2-605 of this Part, if the residue is devised to two (2) or more persons and the share of one (1) of the residuary devisees fails for any reason, his share passes to the other residuary devisee, or to other residuary devisees in proportion to their interests in the residue.