Tell me, do you also document it?

Do you mean document, as in comments? Almost always yes, unless the code itself is so glaringly obvious that it needs no documentation.

If you mean document, as in POD? Then the answer is sometimes. Documenting private and protected methods in POD is only really useful for those who want to subclass your module, and I try to make sure to point that out when I do so as not to confuse.