The right of every public utility, as defined in section 61-129, Idaho Code, furnishing electric, telephone, water or gas service in the state of Idaho, to issue, assume or guarantee securities and to issue mortgages, deeds of trust or other instruments of security with respect to its property situated within the state of Idaho, is hereby subjected to the regulation and supervision of the public utilities commission of the state of Idaho, as hereinafter set forth in this act. Such public utility when authorized by order of the commission and not otherwise, may issue stocks and stock certificates and may issue, assume or guarantee bonds or other securities payable at periods of more than twelve (12) months after the date thereof, for the following purposes; for the acquisition of property; for the construction, completion, extension or improvement of its facilities; for the improvement or maintenance of its service; for the discharge or lawful refunding of its obligations; for the reimbursement of moneys actually expended for said purposes from income or from other moneys in the treasury not secured by or obtained from the issue, assumption or guarantee of securities; or for any other purpose approved by the commission, provided, however, this section shall not apply to any telephone corporation when three-fourths (3/4) or more of the total gross revenue of such corporation is derived from sources outside the state of Idaho.