The stock market was pretty quiet on Monday, with major stock indexes finishing the day mixed. The Dow Jones Industrial Average lost ground, but broader benchmarks generally rose slightly as investors tried to weigh the risks of future surprises on the trade and economic fronts against the possibility of further growth for the U.S. economy. Some companies had good news that sent their share prices higher. NuVasive (NUVA), Avis Budget Group (CAR -3.32%), and Insperity (NSP -2.69%) were among the top performers. Here's why they did so well.

Check out the latest Insperity, Avis, and NuVasive earnings call transcripts.

NuVasive could be a target

Shares of NuVasive rose 13% on speculation that the company might be a takeover target. Reports indicated that medical device giant Smith & Nephew (SNN -0.77%) might be having discussions with the surgical device specialist, with some putting the potential price tag of a deal at around $3 billion. Today's gain put the total market capitalization for NuVasive at just under $2.9 billion, indicating that there might not be a lot more upside for investors hoping for a formal acquisition bid to materialize. Nevertheless, the company has been optimistic about its future, and it might be that Smith & Nephew is interested in sharing in NuVasive's potential.

Several surgical tables with image displays, lighting, digital displays, and other instruments.

Image source: NuVasive.

Avis gets an upgrade

Avis Budget Group saw its stock climb 7% after the rental car giant got an upgrade from stock analysts at Goldman Sachs. Goldman upgraded its rating on Avis all the way from sell to buy, putting a price target of $35 per share on the stock. The analysts believe that Avis is doing a good job both with its primary rental car business and with reselling vehicles that it's put through a full cycle of rentals. With the stock currently priced at far less than 10 times earnings, even tepid growth would be enough to make Avis Budget shares look attractive.

Insperity gets inspired

Finally, shares of Insperity jumped 19%. The provider of human resources and business solutions said that adjusted earnings climbed 25% in the fourth quarter of 2018 compared to the year-earlier period, as accelerating growth in worksite employee counts helped to push the business forward. The company also released favorable guidance for 2019, saying that it expects another 14% to 16% increase in average worksite employees and even greater bottom-line growth. With strong retention and a good environment in the labor market, conditions are working in Insperity's favor.