Security Service Federal Credit Union has been open since 1956. It's the 2nd largest credit union in Texas and the 7th largest in the United States with assets totaling $9.65 Billion and providing banking services to more than 785,000 members. Membership: The credit union is a member-owned financial cooperative providing financial banking services to multiple member groups, but primarily serves the military, i.e. members in the armed forces. Membership is also open to immediate family of current members.