Which of the following is NOT listed as a notable private insurance company?

Kaiser Permanente is often considered a unique entity in the health insurance landscape because it operates as both an insurance provider and a healthcare provider. This integrated model distinguishes Kaiser from traditional private insurance companies like Aetna, Cigna, and Humana, which primarily focus on offering insurance coverage. Aetna, Cigna, and Humana have extensive networks for purchasing insurance plans, while Kaiser Permanente's model includes both the financing of care and the delivery of care through its own facilities and providers. This comprehensive approach may lead to it being perceived differently in discussions about notable private insurance companies.

This unique structure does place Kaiser Permanente outside the traditional definition of "notable private insurance companies," which usually emphasize those that primarily sell insurance rather than deliver healthcare services as well.