In the DC universe (whether it's post Infinite Crisis Multiverse or New 52) Batman is not a metahuman. However despite that, Batman has almost always been described as the world's greatest detective who has a Genius Level Intellect.
Has it ever been described by DC, in any comic, how Batman developed genius level intellect?
IIRC, they talk about how he developed his other talents but they don't talk about how he developed his intellect.
For example (we learn from The Dark Knight) Ra's al Gul trained Bruce Wayne in every aspect of Ninjutsu. Similarly Batman was trained by Zatara, a stage magician to give the illusion of disappearing.
So, did Batman/Bruce Wayne receive similar training from any individual/s that helped him to develop his intellect,did he acquire genius level intellect all by himself or was he just born with it?