Idaho Code § 41-2139
There shall be a provision as follows: a policy delivered or issued for delivery in this state more than one hundred twenty (120) days after the effective date of this act under which coverage of a dependent of an insured terminates at a specified age shall, with respect to an unmarried child who is incapable of self-sustaining employment by reason of intellectual disability or physical disability and who became so incapable prior to attainment of the limiting age and who is chiefly dependent upon such insured for support and maintenance, not so terminate while the policy remains in force and the dependent remains in such condition, if the insured has within thirty-one (31) days of such dependent's attainment of the limiting age submitted proof of such dependent's incapacity as described herein. The insurer may require at reasonable intervals during the two (2) years following the child's attainment of the limiting age subsequent proof of the child's disability and dependency. After the two (2) year period, such subsequent proof may not be required more than once each year.
Idaho Code § 41-2139