Securian Financial announced Monday it is acquiring Empyrean Benefit Solutions, a Houston-based employee benefits enrollment and human resources administration company.

Terms of the deal were not disclosed but it is likely one of St. Paul-based Securian's largest deals in the last four years and should help Securian solidify its position in Fortune's annual list of 500 largest public companies. The deal is expected to close by the end of the year.

"It is a significant strategic investment that complements Securian Financial's broad lineup of innovative employee benefits solutions and opens new growth opportunities for both our customers and us," said Securian's chairman, president and chief executive Chris Hilger in a statement.

The deal adds Empyrean's 600 employees to the approximately 5,600 employees Securian has in the U.S. and Canada. Most of Empyrean's employees are at their headquarters in Houston and offices in Nashville and Minneapolis.

The Minneapolis office was thanks to Empyrean's acquisition of Minneapolis-based Bloom Health in 2016.

Empyrean was founded in 2006 and it now helps more than 400 employers and 3.6 million participants reap the full value of benefit programsthrough its platform that eases the complexity of employee benefit programs and is scalable for growing companies.

Securian Financial is a mutual holding company and the third-largest direct writer of group life insurance. Securian and also offers group accidental death and dismemberment (AD&D), accident, critical illness and hospital indemnity insurance. They disclose financial data for members which qualifies them for the Fortune 500 list.

This latest deal by Securian may help it cement its position as a Fortune 500 company. St. Paul-based Securian has been steadily climbing the Fortune 500 rankings. Securian made its debut in the 500 at #462 in 2018 after climbing steadily up the list. They were ranked #602 in 2015, then #551 in 2016, #532 in 2017 and #462 in 2018 before slipping to #506 on Fortune's most recent list.