Risk of a type which affects each individual case largely independent of others. This could apply to the risk of an individual dying, of a house catching fire, or a car being involved in an accident, during any period. If risk is idiosyncratic an insurance company can insure customers while keeping its own overall risk exposure relatively small. The same argument applies to investment portfolios: idiosyncratic risks in asset returns tend to cancel out in a diversified portfolio. This is contrasted with market risk, where events such as a slump, a flu epidemic, or a hurricane affect large numbers of individuals in a similar manner.