The companies said Thursday that Altice had agreed to pay $34.90 a share for Cablevision, making the deal worth $17.7 billion including debt. The price represents a 22% premium over Cablevision's closing price Wednesday.

The acquisition was first reported Wednesday evening by the New York Times and the Wall Street Journal.

Altice, well-known in Europe but not in the United States, has been seeking to expand its footprint stateside, and Cablevision will help do that.

Shares in Altice gained nearly 7% in Amsterdam in early trade Thursday. The company said it was putting $3.3 billion of cash into the deal, while the remainder of the acquisition would be financed by Cablevision cash and debt.

Cablevision (CVC) provides cable and Internet to about 3 million homes, mostly in and around New York, especially on Long Island.