Charles Schwab on Thursday said it completed its acquisition of online options brokerage company OptionsXpress Holdings, Inc. for an estimated $1 billion.

Schwab already offers options trading through its discount brokerage, and bought OptionsExpress to broaden its reach in the options trading market.

Shareholders of OptionsXpress, which provides brokerage services for equity options and futures, will receive 1.02 shares of Schwab stock for each share of OptionsXpress. Schwab said it expects the acquisition to boost earnings over the first year of combined operations through cost savings.

OptionsXpress had 397,400 client accounts, $8.4 billion in client assets and a 12-month average of 44,900 daily revenue trades as of June 30.

Schwab is one of the nation's largest brokerage firms in terms of client assets, which totaled $1.66 trillion as of June 30. It serves more than 10 million individual, independent advisor client and retirement plan participant accounts.