Tokio Marine Holdings Inc., the nation's second-largest casualty insurer, on Wednesday agreed to buy Delphi Financial Group Inc. for $2.7 billion in its second U.S. acquisition in three years.

The Tokyo-based company will pay $43.875 for each of Delphi's Class A shares and $52.875 for every Class B share in cash, it said in a statement. The takeover is expected to close in the second quarter next year, the companies said in a joint statement.

Tokio Marine has spent more than $6 billion since 2002 on purchases in countries ranging from the U.K. to China as a shrinking population erodes the domestic market.

The company, which bought Philadelphia Consolidated Holding Corp. for $4.7 billion in 2008 in the biggest acquisition by a Japanese insurer, said the latest transaction would strengthen its existing business in the U.S. and offer a platform for a new life insurance unit in the country.

"Tokio Marine Group has been seeking continued expansion of its international insurance business as a major driving force of its mid- to long-term growth strategy," Shuzo Sumi, president of Tokio Marine, said in the statement.