Key TakeawaysIf approved, Capital One's acquisition of Discover would be the fifth-largest deal ever between U.S. banks in mergers and acquisitions history.JPMorgan Chase's acquisition of Bank One in 2004 was the largest to date at $56.88 billion, followed by Bank of America's purchase of FleetBoston Financial for $47.69 billion that same year.Citicorp and Travelers Insurance Group's 1998 merger creating Citigroup in a $36.03 billion deal was the fourth largest.Discover Financial Services (DFS) shares surge ...