You have configured your service provider to use the persistent name ID format.
For more information, see Configuring Identity Federation with Persistent Pseudonyms.
A given persistent name ID exists only once per user pairing between an identity provider and a service provider. You can configure a group of service providers, called an affiliation, to share a persistent name ID for each user. All service providers that take part in the affiliation identify themselves to the identity provider with an affiliation ID. If the service providers are members of the same affiliation, the identity provider sends the persistent name ID saved for that user for the affiliation.
Configure any other service providers that are to participate in the affiliation to use the same affiliation ID.
Configure the identity provider to use a persistent name ID for the affiliation.
For more information, see the documentation for your provider vendor.