Minn. Stat. § 37.34

The society may contract with the holders of any of its bonds as to the custody, collection, securing, investment, and payment of money of the society or money held in trust or otherwise for the payment of bonds, and to carry out the contract. Money held in trust or otherwise for the payment of bonds or in any way to secure bonds and deposits of the money may be secured in the same manner as money of the society, and all banks and trust companies are authorized to give security for the deposits.