In what format should we mark off decimals and/or thousands and millions?

Numbers in iXBRL need to be formatted in the way of the language the file is published in, but when you're using the ParsePort XBRL Converter, you don't need to worry about that.

Our system doesn't care if you feed it with an English report where you would mark off thousands and millions with commas, and decimals with full stops, a Danish report where it's the other way around, or a French or Swedish report where thousands and millions are marked off with spaces instead.

As long as you are consistent with the formatting in your PDF, you can choose whichever version you want. 

For your Excel file the thousand and million separators are selected based on your system settings, but as long as the system displays the separators, you don't need to worry about whether it is commas, full stops or spaces.