Where an arbitration panel based its decision on documents outside of an agreement, it exceeded its authority.The 7th U.S. Circuit Court of Appeals reversed a decision by U.S. District Judge Harry D. Leinenweber.In 2011, Bankers Life & Casualty Insurance Co. leased office space at 600 W. Chicago Ave.. Its lease was set to expire in 2018. Another tenant in the building was Groupon. Groupon needed more office space so, CBRE, a large real estate company, approached Bankers about the possibility of Bankers&rsquo …