There are several types of documentation; end user (how to use it) doc, technical (how does it work in detail) doc, over view (how does it work) doc, individual program doc, procedural doc, data flow doc (data movement without details on its transformation), …
You should find out if your work place has any standards for said documentation.
you might ask for some doc (from another effort) that the bosses like and/or that meets the requirements.
Good doc will convey the proper level of information and detail. An overview for managers is different from program specifications.