This web site provides examples of XBRL reports.  A basic introduction to XBRL is also provided.

Short introduction to XBRL from the Chartered Accountants Organization. This introduction covers XBRL from a chartered accountant perspective. This web site is linked from the XBRL US web site.

This is an academic XBRL Resources website providing access information on XBRL resources, conferences, forums, and academic competitions.

This is Q&A website with a catch "clear answers for common questions," and this particular page provides a concise, single-page answer to the question: "What is XBRL?" It also provides links to related sources.