I need to find an idiom for the following situation.
I am talking to the HR department about a particular policy. I did not know about the policy beforehand and HR had never explained it to me. For HR people, all the policies are obvious, I presume.
I want to say to HR:
HR people discuss HR policies with employees on a daily basis and so for them the relevant facts are very obvious or need no explanation but for me they are completely new
I want to replace obvious or needs no explanation with an idiom or phrase.