Brennan died Thursday night in Burr Ridge after a brief illness, the Chicago Tribune reported Saturday.

Brennan helped build Sears into a financial conglomerate for insurance, investment services and real estate transactions in the 1980s and then sold off most of those companies in the 1990s, generating large returns for investors, the Tribune reported.

After retiring from Sears in 1995, Brennan remained active in the corporate world and helped American Airlines avoid bankruptcy in 2003 when he became American's executive chairman and president. Brennan also served on the boards of 3M Co., Exelon Corp. (NYSE:EXC), McDonald's Corp., and Rush University Medical Center and as chairman of DePaul University and Marquette University.

Brennan is survived by his wife, Lois, and six children.