how to map custom xbrl taxonomy tags

Question

I'm working on a Python app that reads the sec.gov quarterly reports documents and store the parsed information in a database.

In many quarterly and annual reports there are custom XBRL tags that clearly refer to a standard GAAP item.

For example, in the following 10-Q, in the Liabilities section there is an entry "Notes payable – floor plan" that is tagged as onew:NotePayableFloorPlan. This is clearly a Short-Term Debt but there is no information about it in the calculation or presentation XML file that classify it. The only information I was able to find is that this is part of the LiabilitiesCurrentAbstract concept, but this is a very generic classification.

How do I automatically find out the correspondence between custom taxonomy and standard accounting concepts ?

https://www.sec.gov/ix?doc=/Archives/edgar/data/1772921/000114036122028384/brhc10040150_10q.htm

Answer 1

I suggest looking into the work by Charles Hoffman, CPA, who contributed a taxonomy of fundamental accounting concepts (FAC) together with a mapping (provided as an XBRL linkbase) from extension concepts used by filers and sanity-check rules, all machine-automatable.

Maybe a good place to start is here, and there are links to the actual mappings and rules:

http://xbrlsite.azurewebsites.net/2021/library/FundamentalAccountingConcepts.pdf

Answer 2

Unfortunately, the short answer is that this information isn't in the filing. The best you can do is analyse the calculation relationships to determine that this item contributes to Total Current Liabilities.

European filings made under the ESEF programme are required to include "anchoring" relationships (using the wider-narrower relationship type), which associate any filer-specific concepts with the standard concept with the closest accounting meaning, but this is not currently required for US SEC filings.

There are also enhancements planned for the XBRL specification (Calculations v2.0) that would allow filers to create calculation relationships to unreported concepts. This would allow filers to create the calculation relationships to the nearest standard concept to which the extension contributes, rather than the nearest reported concept.