Rising media company Nexstar Broadcasting's (NXST) stock hit an all-time high early Thursday after it reported strong fourth-quarter earnings before the market opened and added two more TV stations, the latest in a series of purchases. Nexstar's Q4 earnings jumped to 70 cents per share from 11 cents a year ago. That easily beat analyst consensus of 56 cents as advertising revenue rose, boosted by political ads in an election year. Revenue popped