My (admittedly aged) experience with XBRL is that each company was able to define its own fields/format within that spec, and that most didn't agree on common names for common fields. Parsing it wasn't fun.
I have spotty education on the matter but I believe they all conform to a FASB taxonomy so there is at least a list of possible tags in use. I do wonder if any of the big data vendors actually use this though.