IDEA is not a certification agency. It is a membership organization. They offer workshops and events, tools for professional development, networking opportunities, etc.
There are huge numbers of organizations offering certifications in pretty much any area you can imagine.
First figure out what you want to do with certification. Do you, or do you want to teach group ex classes? Do you or do you want to do individual training? Lifestyle coaching? Kickboxing? Pilates?
Some people go the route of getting as many certifications as possible in as many subjects as possible. Some prefer to get the best ones they can in a few areas. Myself I prefer the later… It takes a lot of time and money to keep up with each thing you add. On the other hand if you are a studio owner, for example, or working in a place where there are not a lot of other fitness businesses, it might be helpful to have a general understanding of a lot of things.
Also recognize that for some things you will not be able just to take a test and be certified. You will also need to complete training in some cases.
Look for certifications that are NCCA certified. ACE is very well regarded, but there are others. Once you know what you want to do with the certification, and you have pinpointed a training program or test you might check back here with a question about a specific certification or training to see if anyone has done it and can recommend it.