(Reuters) -Arthur J. Gallagher said on Monday it has agreed to acquire insurance broker AssuredPartners in a $13.45 billion deal, as it looks to bolster its presence in the vast and fast-growing middle-market segment.

Gallagher follows in the footsteps of rival insurance brokers Aon and Marsh McLennan, which have struck big deals over the last 12 months to expand their foothold in the middle-market insurance business.

The middle-market insurance business provides services designed for mid-sized firms that make between $10 million and $1 billion in annual revenue.

Gallagher expects to finance the deal - likely to close during the first quarter of 2025 - through a mix of cash, debt and equity.

Orlando, Florida-based AssuredPartners was founded in 2011 by private equity firm GTCR. Since then, the company has become one of the largest insurance brokers in the United States.

GTCR sold the company to Apax Partners in 2015. But again in 2019, an investor group led by GTCR agreed to acquire AssuredPartners from Apax, which held a minority stake in the company.

Last year, Gallagher acquired Cadence Bank's insurance brokerage unit for $904 million.