Warren Buffett has famously stated that investors should only invest in businesses that they understand. In recent years, that has become an almost impossible hurdle for the nation's largest banks. 

However, moving down the list of major U.S. banks, there are still some notable examples of simple, old-school banks worthy of a closer look. From BB&T (NYSE:BBT) to KeyCorp (NYSE:KEY) to U.S. Bancorp (NYSE:USB), regional banks offer the opportunity for solid investments in banks without the complexity, risk, and systemic regulation.

In the video below, Motley Fool contributor Jay Jenkins takes a closer look at another traditional regional bank, People's United Financial (NASDAQ:PBCT), digging into the income statement to see exactly how they make money.