Too many values. Not showing all data in Matrix

I'm currently facing a big problem. Not all my data gets displayed in the Matrix. I have to display it (customer requirement). There are after the drill down just around 200 cols and not all of them are displayed. I've read a lot of articles where other users have similar problems but nothing seemed to work. Here is what my table looks like:

The rows are my cost centers + work packages and the cols are the employees. Is it possible to show all of the employees? If I just put the employees in the rows section everything works, so why doesn't that work for the col section?