As the name says, Trace to Report allows you to trace/track any returned XBRL data back to its source document. Point to the value you wanted to view the source document and click "Trace to Report" tab in XBRLAnalyst ribbon.
Alternatively, you can also use "Right Click" to the value and choose "Trace to XBRL Report" from the drop-down list.
Please note that this only applies to values with "Annotations". To add annotations to your exported or returned values, please set it in XBRLAnalyst Settings.