So here is a documented case where XBRL contributed to detecting and correcting an accounting error. Click on the image below to get a larger image after you read this. In this public company's March 31, 2017 income statement (on the LEFT) they ordered their income statement line items one way. Then, in the June 30, 2017 income statement (on the RIGHT) they ordered them a different way.
The NEW way is consistent with literally all public companies that report these line items and consistent with the US GAAP Financial Reporting XBRL Taxonomy. The OLD way was not.
(Click image for larger view)This inconsistency was detected using the fundamental accounting concept relations validation continuity cross checks. Now, they still don't have their XBRL-based representation correct. They have some concept selection issues that need to be fixed.