Cooper Health System agreed to pay at least $7.5 million for a 20 percent stake in AmeriHealth New Jersey, according to the Camden system's consolidated financial statement for 2012, released Tuesday.

Cooper and Amerihealth's parent, Independence Blue Cross, announced the deal April 10, but the price was not disclosed at that time.

Cooper said its investment could increase if the New Jersey Department of Banking and Insurance requires a higher level of capital in the joint venture, which will be set up as a limited liability company.

If regulators approve the arrangement, AmeriHealth and Cooper will develop lower-cost health-insurance offerings, executives said.

AmeriHealth has about 5 percent of the commercial health-insurance market in New Jersey.