Tokio Marine Holdings Inc. agreed to buy HCC Insurance Holdings Inc. for about $7.5 billion in the biggest acquisition by a Japanese insurer, stepping up an overseas expansion to counter stagnation at home.

Tokio Marine will pay $78 in cash per share for Houston, Texas-based HCC, according to a statement on Wednesday. That’s a 37.6 percent premium to the latest closing price.

Japanese insurers are looking for ways to spread risks and increase revenues overseas as an aging population saps demand for policies and natural disasters lead to higher payouts. To that end, they’ve announced $27.5 billion of acquisitions abroad in the past five years, Bloomberg-compiled data show.

Before the latest deal, Tokio Marine had made $8.8 billion of purchases in North America, according to the data. The biggest was the 2008 purchase of Philadelphia Consolidated Holding Corp., valued at $4.6 billion.