 NEW YORK--BUSINESS WIRE--Halper Sadeh LLP, a global investor rights law firm, is investigating whether the merger of First Interstate BancSystem, Inc. NASDAQ: FIBK and Great Western Bancorp, Inc. is fair to First Interstate shareholders. Following completion of the transaction, First Interstate shareholders will collectively own 57 of the combined company. Halper Sadeh encourages First Interstate shareholders to click here to learn more about their legal rights and options or contact Danie 