Idaho Code § 62-102

Railroad corporations may borrow on the credit of the corporation, and under such regulations and restrictions as the directors thereof may impose, such sums of money as may be necessary for constructing, completing, equipping, extending and improving their railroad, and all else relative thereto, and for leasing, purchasing or operating the whole or any part of the railroad of any other railroad corporation, together with the franchises, powers, immunities, and all other property or appurtenances appertaining thereto, and may issue and dispose of bonds and promissory notes therefor bearing interest at a rate not exceeding ten per cent (10%) per annum, and may also issue bonds and promissory notes bearing interest not in excess of the rate aforesaid, in payment of any debts or contracts for constructing, completing, equipping, extending and improving their road, and all else relative thereto, and for leasing, purchasing or operating the whole or any part of the railroad of any other railroad corporation, together with the franchises, powers, immunities and all other property or appurtenances appertaining thereto and to secure the payment of any or all of such bonds and notes, they may mortgage their corporate property and franchises.