U.S. stocks wrapped up Monday's session in negative territory as investors parsed a slew of corporate earnings reports and oil prices fell almost 1%. Pandora (P) shares declined 3.6% after analysts at Bank of America Merrill Lynch downgraded the stock to underperform from neutral, citing increased competition from other music streaming platforms such as Spotify, Apple and Google. The analysts reduced their price target on the stock to $9 from $14. The stock trades at $12.38. Quality Systems (QSII) shares gained 7.9% after a report from DealReporter said the company has hired UBS to advise on a possible sale. TheStreet's Scott Gamm reports from Wall Street.