The authority may invest the proceeds from the sale of a series of obligations or any funds related to the series in such securities and other investments, whether or not any such investment or reinvestment is authorized under any other law of the state, as may be provided in the proceedings under which the series of obligations are authorized to be issued. The authority may invest any other funds in obligations of the federal government, the state or of any municipality thereof or obligations of agencies of the federal government; in bonds, notes, certificates of indebtedness, treasury bills or other securities constituting direct obligations of the United States of America; in certificates of deposit or time deposits constituting direct obligations of any bank in Idaho; provided, however, that investments may be made only in those certificates of deposit or time deposits in banks which are insured by the federal deposit insurance corporation, if then in existence, and may exceed the maximum of such insurance; or in short term discount obligations of the federal national mortgage association. Any such securities may be purchased at the offering or market price thereof at the time of such purchase. The authority may invest any other funds with such maturities as the authority shall determine provided that such maturities are on a date or dates prior to the time when, in the judgment of the authority, the funds so invested will be required for expenditure. The express judgment of the authority as to the time when any such funds will be required for expenditure or be redeemable is final and conclusive.