Centene, a major health insurer based in St. Louis, is paying $17.3 billion in cash and stock to purchase WellCare Health Plans, a provider of government-sponsored health care programs, including Medicaid.

The merger has been approved by both companies’ boards of directors and is expected to be completed in the first half of 2020. Together, the merged company will service about 22 million members with pro forma revenues of about $97 billion annually.

“With the addition of WellCare, we expect to bolster and diversify our product offerings, increase our scale and have access to new markets, which will in turn, enable us to continue investing in technology and better serve members with innovative programs designed to meet their needs,” said Centene’s chairman and CEO Michael Neidorff in a statement.

UnitedHealth Group, the nation’s largest insurer, serves 115 million members and takes in $226 billion annually, ranking it fifth on the Fortune 500 list of largest U.S. companies by revenue.