Insurance bought by insurers. A reinsurer assumes part of the risk and part of the premium originally taken by the insurer, known as the primary company. Reinsurance effectively increases an insurer's capital and therefore its capacity to sell more coverage. The business is global and some of the largest reinsurers are based abroad. Reinsurers have their own reinsurers, called retrocessionaires. Reinsurers don’t pay policyholder claims. Instead, they reimburse insurers for claims paid.