Idaho Code § 40-605
Commissioners may lay out new highways within the county as they determine to be necessary. The right-of-way of any highway shall not be less than fifty (50) feet wide, except in exceptional cases. Commissioners may also change the width or location or straighten lines of any highway under their jurisdiction. If, in the laying out, widening, changing or straightening of any highway it shall become necessary to take private property, the commissioners or their director of highways shall cause a survey of the proposed highway to be made, together with an accurate description of the lands required. The commissioners shall endeavor to agree with each owner for the purchase of a right-of-way over his land included within the description. If they are able to agree with the owner, the commissioners may purchase the land out of the county highway fund under their control, and the land shall then be conveyed to the county for the use and purpose of highways.
Idaho Code § 40-605