I would like to use label references for my future amortization expense table so that I can make sure that the row descriptions in the xbrl outline match the table in the document. For this particular table, the row descriptions are years and I tend to forget to go in and manually update the years in the outline each year. Typically, to add a label reference, I click on the appropriate "row" in the outline and drag and drop it over the corresponding row in the table. However, for this table it isn't working. When I drag, it never changes from the red x to the green +. I re-tagged the table using table focus mode, thinking it might be that the whole row needs to be tagged, but that didn't seem to do the trick. Any ideas why this table would be different?