Charles Schwab Corp. on Monday said it had reached an agreement to acquire rival discount broker TD Ameritrade Holdings Corp. in an all-stock deal valued at around $26 billion.

Shares of both companies jumped last week after reports they were in talks. The agreement would see TD Ameritrade AMTD, +1.80% stockholders receive 1.0837 Schwab shares for each TD Ameritrade share, representing a 17% premium over the 30-day volume-weighted average price exchange ratio as of Nov. 29. Schwab shares SCHW, +1.68% were off 0.9% in premarket action on Monday, while Ameritrade shares jumped more than 3%.