Idaho Code § 31-1903
When the interests of the county require it and the board of commissioners of the county deem it for the public good to bond the county to fund or refund the outstanding obligations or indebtedness of the county or bond the county for the purpose of acquiring funds for purchasing a site and erecting a courthouse and jail, a public auditorium or a jail thereon, or for the construction or repair of roads or bridges, or to assist any city or village in said county in constructing a free bridge over any navigable stream within, or partly within, or adjoining, the limits of any such city or village, or for purchasing, improving and equipping air navigation facilities as defined in chapter 4, title 21, Idaho Code, which facilities may be wholly or partly within or without the limits of such county, or wholly or partly within or without the state of Idaho, or for purchasing public open-space land and/or easements for scenic and recreational purposes, or for any one (1) or more said purposes, and the indebtedness or liability of the county that may be created by the bonding, funding or refunding aforesaid, or in purchasing a site and erecting a courthouse and jail, a public auditorium or a jail thereon, and for the construction or repair of roads or bridges, or for assisting any city or village in the construction of any such free bridge as aforesaid, or for purchasing, improving and equipping air navigation facilities, or for purchasing public open-space land and/or easements for scenic and recreational purposes, or for any one (1) or more of said purposes, exceeds the income or revenue of the county for that year, the board of commissioners may issue bonds of the county as provided by sections 31-1901 and 31-1902, Idaho Code, and by the "municipal bond law" of the state of Idaho: provided, that the issuance of such bonds, except funding or refunding bonds, be first authorized by a vote of two-thirds (2/3) of the qualified electors of the county, voting at an election held, subject to the provisions of section 34-106, Idaho Code, for that purpose, as hereinafter provided and as provided in the "municipal bond law" and, provided, further, that before the board of county commissioners shall issue any bonds to fund or refund the indebtedness of the county as in the section provided, they shall deduct from the legal indebtedness of the county, at the time of the issue of said bonds, the cash on hand in the county treasury applicable to the discharge of said indebtedness, and may issue bonds for the remainder of the indebtedness.
Idaho Code § 31-1903