CBS Corp. agreed to merge with Viacom Inc. in an $11.7 billion transaction, following years of talks and negotiations between the U.S. media giants.

The all-stock deal, announced Tuesday, unites the most-watched U.S. broadcast network with the parent of Paramount Pictures and cable channels such as MTV and Nickelodeon.

According to the announced deal, CBS shareholders will get 61% of the combined company, with the remainder going to Viacom investors. Each Viacom share and will convert into 0.59625 of a CBS share.

Shari Redstone, whose family investment vehicle National Amusements Inc. controls both companies, will become chairwoman of the combined entity. Viacom Chief Executive Officer Bob Bakish will lead the business as CEO.

The transaction could give the combined entity much greater position in negotiating deals with pay-TV distributors.

CBS would receive six seats on the 13-member board, while Viacom would get four. Another two would be designated to National Amusements.

CBS shares have lost about 18% since the beginning of 2018, as the broadcaster faced mounting challenges, including the ongoing competition for viewers with the likes of Netflix Inc.