Shares of Triple-S Management, San Juan, Puerto Rico, at last check were 45% higher at $35.01. They touched a 52-week low $17.32 in mid-September.
Under the terms, GuideWell will pay $36 cash for each share of Triple-S Management. That's about a 49% premium to Triple-S Management's 90-day volume-weighted average trading price.
The boards of both companies approved the terms. The acquisition is expected to close in the first half of 2022, subject to conditions including regulatory review and a vote of Triple-S holders.
GuideWell is the parent of Blue Cross and Blue Shield of Florida. GuideWell companies serve more than 45 million people in 45 states.
Florida Blue is the oldest and largest health insurer in Florida, GuideWell said, with more than 5 million members across all 67 counties in the state.
Triple-S Management has more than 1 million consumers in Puerto Rico.
"The transaction expands GuideWell's core insurance operations," Pat Geraghty, president and CEO of GuideWell and Florida Blue, said in a statement.
He added: "With Puerto Rico's outlook strengthening, and Florida experiencing fast-paced growth, especially in its Puerto Rican and Hispanic populations, this is a natural next step."