Idaho Code § 34-405

For the purpose of voting, no person shall be deemed to have gained or lost a residence by reason of his absence while employed in the service of this state or the United States, while a student of any institution of learning, while kept at any state institution at public expense, nor absent from the state with the intent to have this state remain his residence. If a person is absent from this state but intends to maintain his residence for voting purposes here, he shall not register to vote in any other state during his absence.