Insurance that protects insurance companies against having too much risk is known as what?

Reinsurance is the correct answer because it involves an insurance company transferring portions of its risk to another insurance company. This mechanism allows the primary insurer to protect itself from large claims or financial losses that could occur from underwriting too many policies or facing catastrophic events. By doing so, reinsurance effectively stabilizes the insurance market, allowing insurers to manage their risk exposure and continue providing coverage to policyholders without overly concentrating risk.

In the context of the other terms, retrocession refers to when a reinsurer passes on a portion of the risk it has assumed to another reinsurer, which is a secondary level of risk transfer and not the primary function intended for insurance companies. Underwriting relates to the process of evaluating and determining the risk profile of potential policyholders to set appropriate premiums, rather than protecting insurers from excessive risks. Co-insurance is a term commonly used in health insurance and property insurance that refers to the sharing of costs between the insurer and the insured, rather than a mechanism for risk management among insurers. Thus, reinsurance stands out as the appropriate choice for protecting insurance companies from accumulating excessive risk.