Inline XBRL allows nested and double tagging of narrative text so that a report can be written as naturally as possible and a machine can accurately extract the required information to answer a particular question.
As a taxonomy designer, it can be useful to have a more general concept to capture large text blocks and more-specific concepts to capture more precise information.
Example
Narrative disclosures (text rather than numbers) can be tagged so that information is machine extractable as well as human readable. Those tags can be nested. An example with two different tags (blue dotted highlight is one tag, blue solid highlight is another tag):

An XBRL viewer can then show the taxonomy details relating to the tag:

Links
- Example filing with narrative tagging and below are direct links to different narrative tags: