Hartford Financial Services Group Inc. will no longer insure or invest in companies that generate more than a quarter of their revenues from thermal coal mining or more than 25% of their energy production from coal itself.

The company will also stop insuring and investing in companies that generate more than 25% of their revenues directly from the extraction of oil from tar sands.

The Hartford will phase out existing underwriting relationships and divest publicly traded investments that exceed the threshold by 2023. The insurer's new policy includes exceptions for business lines that cover employees, such as disability, life and other voluntary products offered by its group benefits division.