A study (A Comparison of XBRL Filings to Corporate 10-Ks - Evidence from the Voluntary Filing Program) finds what they call serious errors in XBRL filings to the SEC Voluntary Filing Program (VFP).
Here is the abstract of the research paper:
The SEC has mandated a phase-in of XBRL filings beginning June 2009 for accelerated filers. Although companies have limited legal liability for initial filings, registrants may suffer reputational and other risks should the filings include errors. To assess the likelihood of material errors, we evaluate the accuracy of XBRL filings for 22 companies participating in the SEC.s voluntary filing program in 2006. Results of a comparison of XBRL filings to Forms 10-K reveal multiple errors in signage, amounts, labeling, and classification. These errors are serious because since XBRL data is computer-readable, users will not visually recognize the errors, especially when using XBRL analysis software. Although XBRL software and taxonomy have improved since 2006, the potential for some errors remains. The SEC, registrants, and accountants need to take note of the complexities of XBRL tagging and identify solutions (e.g., assurance, training) to ensure successful adoption.
The general types of error discovered and reported in this study includes:
- Missing elements and amounts
- Incorrect amounts
- Sign flips (i.e. reported as a positive when it should be a negative value as an example)
- Duplication of items
- Incorrect classifications
- Incorrect tagging (labeling)
The VFP did not really do a lot in the way of validating submissions. Nor did the SEC seem to crack down on people whose submissions contained errors. This probably will not be the case for the real filing companies make to the SEC. I would suspect that significantly more robust processes will be wrapped around "real" submissions.
Further, the AICPA has issued a statement of position (SOP 09-1) titled Performing Agreed-Upon Procedures Engagements That Address the Completeness, Accuracy, or Consistency of XBRL-Tagged Data. This guidance did not exist during the time that these VFP filings were made. It does now. This will contribute to improving the quality of the filings, at least if CPAs are involved in the process as they need to follow this guidance. While the SOP does not tell you how to create a good XBRL instance, it does help to define "good" by pointing out the things which are not good.
Anyone responsible for creating XBRL instances, whether for SEC filings or any other types of XBRL instances, would benefit from reading this paper. It helps you understand the types of things to look for when reviewing an XBRL instance of any type.