Idaho Code § 58-320

All lands heretofore sold under the provisions of this chapter shall be exempt from taxation for and during the period of time in which the title to said land is vested in the state of Idaho, but the value of the interest therein of the purchaser shall be taxed, which interest shall be assessed for purposes of taxation as other property is assessed and the improvements thereon shall also be taxed. Provided, however, in the case of state land hereafter sold under contract, such land shall be assessed at its full cash value as other property is assessed.