I have many different blog posts that provide information about errors that exist in XBRL-based digital financial reports. Understanding errors and how to avoid them is a good way to learn about XBRL. To make finding these documents easier, I combined all of the best information into this one blog post where you can find all of this documenation.
These are documentation of fundamental accounting concept relations inconsistencies: (April 2017)
These documents show disclosure mechanics errors and other information: