Fidelity National Information Services Inc. FIS said Thursday it is accelerating its plan to split into two companies with an agreement to sell a majority stake in its Worldpay Merchant Solutions business to private-equity funds managed by GTCR in a deal that values Worldpay at $18.5 billion. FIS previously announced plans to spin off its merchant business, which largely consists of Worldpay, into a separate business, a move that would walk back the company’s merger with Worldpay that was announced in early 2019.