Documenting decisions

I work in a small company that is very sparse in documentation and what documentation we have frequently does not provide the information that we need down the road. I there read with interest these blog entries: http://blogs.msdn.com/b/nickmalik/archive/2010/11/20/are-we-documenting-the-wrong-things.aspx, http://duckdown.blogspot.com/2010/11/documentation-cannot-compile-run-or-do.html.