Birmingham-based ProAssurance Corp. is being acquired by the nation’s largest physician-owned medical malpractice insurer.

The Doctors Company will acquire the company for $1.3 billion. The deal is not expected to be closed until the first part of next year.

The deal will create a company with combined assets of $12 billion.

According to documents filed with the Securities and Exchange Commission last week, said that there will be no staffing changes until the deal is completed and a majority of employees will not be required to interview for their current jobs.

If positions are eliminated within the first year after the transaction is closed, employees will be eligible for severance with credit for years of service with ProAssurance.

The Doctors Company is part of TDC Group, the nation’s largest physician-owned provider of insurance and risk management solutions, which has annual revenue of $1.5 billion and more than $8 billion in assets.

“This transaction will deliver significant value to our shareholders,” ProAssurance CEO Ned Rand said in a statement.

“Both ProAssurance and The Doctors Company were founded by physicians in response to the medical liability crisis of the 1970s. Both companies have grown over the years by bringing together other physician-founded companies. This shared history has helped both companies fulfill our shared mission to protect others and given us similar operating philosophies and cultures.”