Captive insurance company
From ACT Wiki
1. Groups of companies - insurance.
A company that is part of a more general commercial group of companies, established primarily to insure the risks of its parent company and other companies in the group.
The owners are the insured.
2. Groups of companies - insurance - wider ownership structures.
Similar companies with a limited range of customers - rather than being part of the general insurance market - but owned by a wider number of corporate shareholders than a single parent company.
The broader shareholder group would still be the primary customers of the captive insurance company.