Add Accounts to Portal Users Merged

I would like to have an Account/Customer field for Idea Portal Users.  That was we can more easily track which customers are submitting ideas rather then looking at domain names.

Example of this, we want to easily be able to run reports on what ideas our main customers have created.  Each customer has multiple users, so we have to look at the domain of the email and filter based on that.  Which is not a scale-able approach.