Except as otherwise provided in this title, no insurer or captive doing business in this State may expose itself to a loss on one risk in an amount exceeding ten percent of its surplus to policyholders. A risk or portion of it which has been reinsured must be deducted in determining the limitation of risk prescribed in this section. As used in this section, "captive" means an insurance company owned by another organization whose exclusive purpose is to insure risks of the parent organization and affiliated companies, or for groups and associations, an insurance organization owned by the insureds whose exclusive purpose is to insure risks of member organizations or group members and their affiliates, or both.