NEW YORK (AP) - Tokio Marine Holdings Inc., Japan's largest insurer, said Wednesday it plans to acquire U.S.-based property and casualty insurance firm Philadelphia Consolidated Holding Corp. for $4.39 billion in cash.

Tokio Marine will pay $61.50 per share in cash for Philadelphia Consolidated, a 73 percent premium to the stock's $35.55 close Tuesday. The total purchase price is based on Philadelphia Consolidated's 71.4 million shares outstanding as of April 30.

Tokio Marine valued the deal at $4.7 billion total. It is expected to close in the fourth quarter, subject to regulatory approvals and other closing conditions.

Philadelphia Consolidated has 47 offices and about 1,400 employees nationwide. Executives of the company said in a statement they planned a "substantial investment" in Tokio Marine stock after the deal closes.

The deal marks the largest acquisition by a Japanese insurance firm in the U.S.

"We believe (in the) strong potential in the U.S. market, and the acquisition is part of our efforts to expand our businesses worldwide," said Hiroyuki Hasegawa, a spokesman for Tokio Marine.

AP Reporter Shino Yuasa in Tokyo contributed to this report.