I wouldn't go that far and define in a glossary what the Customer ID is about. The Glossary should be about terms that are worth of defining, e.g. for offering precision. At least for these terms it makes sense to define a taxonomy to allow finding related information to them (e.g. In SharePoint). In glossary should also appear the context.

It makes sense to add the name of the table of origin, respectively the aliases or alternative terms it appears under, the precision, scale, and uppon case the format, respectively a list with the values it can take or at least a reference to the place where the values are defined. Ideally the data dictionary should reflect the criteria used for assessing attribute's quality.