Hi - yeah, documents are tricky because they can be on multiple object types. My guess is you picked a column that would appear if the document was at the portfolio or program level.
What level do you usually have documents? Like for us, it is at the project level so I use
valuefield=project:portfolio:name
valuefield=project:program:name
If you have them at the task level, you'll want: valuefield=task:project:portfolio:name
If you have them at the issue level, you'll want: valuefield=opTask:project:portfolio:name
Hope that helps.