Cause
In the Mapping table of a Xbrl taxonomy file you can define two xbrl elements (column XbrlId), separated by semicolon. If both elements have the same balance (debit or credit) a message appears.
Solution
Indicate just one element in the column XbrlId or choose elements with different balances, one with debit balance and one with credit balance. You can see the balance type in the table Concepts.