While an existing Aha! non-portal user can navigate from the team area to the ideas portal to add ideas, they cannot login directly into the Private Ideas portal URL using existing credential (does not seem to recognize the login from non-portal). We're using "employee private" domain filtering with self-registration.
Due to security reasons, login credentials between the ideas portal and application are different. At this time, we do not have plans to make updates in this area in an effort to keep high security standards. We hope you can understand.