USAA is unique in that customers must be in the armed forces or be close family members. The company has many insurance options that can be paired with your auto policy. Membership also allows access to other benefits, like banking services. In terms of market share, USAA comes in fifth place.
In general, USAA receives stellar ratings from customers and third-party rating agencies alike, including the top score in The Zebra Customer Satisfaction Survey. If membership is an option for you, the company is definitely worth looking into.