I am getting more and more questions about how to learn XBRL.  Most people want some sort of self study option.  Here are several steps which will get you well on your way to gaining XBRL expertise.

The probability that XBRL will be part of your future is increasing every day.  If you believe that XBRL will be part of your future, you can make the investment of learning about XBRL and gain expertise which not a lot of business people currently posesse and you can use this to set you apart.

If you want to learn about XBRL, I would recommend following these steps:

1. Read XBRL for Dummies.  Chapter 1 is a must, it provides in about 20 pages a comprehensive explanation of XBRL.  Chapter 4 provides an XBRL Primer.  There is a lot there for both business readers and technical readers.
2. If you want more detail, read Financial Reporting Using XBRL.  This book is a little dated, but it provides the next level of deal for understanding XBRL. You can get a printed version (for the price of shipping) or download PDFs.
3. Get your hands dirty.  Chapter 11 of Financial Reporting Using XBRL is called Modeling Financial Reporting Concepts in Taxonomies. If you build each one of these rather simple fragments of XBRL you will really begin to see what XBRL is all about and how to use it. You can see each of these small samples here.
4. If you need XBRL tools, see this web page. (See the section on XBRL software).
5. If you want to implement XBRL in production systems, be sure to read about XBRL Simple Application Profile. This helps you understand some realities about working with XBRL. These issues are also summarized in XBRL for Dummies, see Chapter 2 and Chapter 12 in particular.
6. Follow this blog.  This blog is a source for the most current information, ideas, understanding issues, working around problems, etc.  It may be a lot of work, but that is what it takes to become expert in anything: hard work.  There are no short cuts.

If you want more or options when it comes to learning XBRL, check out Mastering XBRL.