As mentioned in one of the comments, you should first search for 'different' Gods on different websites and select each God and verify anything irrational in all those Gods. After that, you can choose one 'Rational God' and ask this question. Otherwise it'd become a beat around the bush.
If you choose one or more things as the idea or concept of God you will have to regard all the other things as the idea or concept of another God. [We can't rule out the possibility of another God or gods (since there are similar creations or concepts in this world)]. Which God would you choose then for this question?
If you choose a particular idea, concept, category or religion only as the concept of God, that would also become a folly....since the supplement for that concept and the complement of that concept must be of another God's. Then also there must be another God or gods.
So, when we think of an (external) creator of ideas or concepts (God), there pops up some contradictions.
We perceive this world through our senses. Knowingly or unknowingly we admit only the things perceived through our 5 sense organs (Some forms of lights, sounds, smells etc that we can't perceive with our sense organs are transformed in another form. But they also are for helping these senses only.)
The senses, brain etc create a feeling that there is creation here. What about the situation if the number or senses increased or decreased? Then, would our understanding be like this...? Actually, we can't even imagine such a situation.
If you can imagine these senses, brain etc as somebody's creations, ideas or concepts, you will have to search them also. This is not possible with your senses.
The things, ideas and concepts that we understand with our mortal sense organs and brain are never the Ultimate Truth.
So, if you believe (this logic) or not, you will have to assume that there is no creation. When you realize yourself you will understand whether there is any real creation here. Then you wouldn't need to ask this question.
The notion that mAyA has no reality in itself, and that brahman is the only real, allows the sRshTi-dRshTi vAdin to "graduate", so to speak, to ajAtivAda, the view that no creation really occurred ever.