Check out which companies are making headlines after the bell on Thursday:
Costco's stock ticked up about 2 percent in after-hours trade Thursday. The wholesale retail giant reported quarterly earnings of $1.77 per share, beating analyst estimates of $1.73 per share. It missed on revenue, however, reporting $36.56 billion, compared to analyst estimates of $36.81 billion.
Shares of Mentor Graphics spiked 6 percent after the bell, following Elliott Management's disclosure that it was doubling its stake in the software company. Elliott upped its stake to 8 percent from its original 4 percent, saying the stock is "deeply undervalued." Billionaire investor Carl Icahn exited his stake in the company earlier this year.
Alcoa shares jumped nearly 2 percent after the board announced an official date for the company's split. The separation will take effect before the opening of the market on Nov. 1. The company had previously announced it would take place in the second half of the year. The engineering and manufacturing company will become two independent and publicly-traded companies: Alcoa and Arconic.
Shares of Wells Fargo fell about half a percent after the bell Thursday amid a report that Warren Buffett had spoken with the board of directors, asking for "radical transformation." Buffet denied the report to CNBC, saying he's spoken to no one else on the board, besides CEO John Stumpf. "It's dead wrong to imply I've spoken to the board directly," Buffett said. "Going to the board implies I've gone around Stumpf, the guy who is under fire."