Idaho Code § 15-6-403
Any estate in personal property held by a husband and wife as community property with right of survivorship shall, upon the death of one (1) spouse, transfer and belong solely to the surviving spouse as a nontestamentary disposition at death. The first deceased spouse does not have a right of disposition at death of any interest in community property with right of survivorship. An estate in community property with right of survivorship is created by a written grant, transfer or devise to a husband and wife when expressly declared in the written grant, transfer or devise to be an estate in community property with right of survivorship. An estate in community property with right of survivorship may also be created by written grant or transfer from a husband and wife, when holding title as community property or otherwise, to themselves or from either husband or wife to both husband and wife when expressly declared in the written grant, transfer or devise to be an estate in community property with right of survivorship. The grant, transfer or devise is effective upon delivery, while both husband and wife are alive, to the entity at which the personal property is held. A written grant, transfer or devise includes the making of the appropriate choice on a form from the entity at which the personal property is held.
Idaho Code § 15-6-403