SEI-US Employees Federal Credit Union has been open since 1935. It's the 24th largest credit union in Idaho with assets totaling $21.98 Million and providing banking services to more than 3,000 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.