Dr. Ghislain Fourny, a computer scientist for 28msec, has written a freely available book about XBRL oriented toward professional software engineers, architects, and developers: The XBRL Book: Technical, Simple and Precise.
Ghislain brief description of the book is:
Put simply, this book is the simple and precise starting point I wish I had had when I first encountered XBRL. Most of these pages do not require any XML or XML Schema knowledge, except for the one section in each chapter that goes into details about the syntax -- but the latter can easily be skipped on a first read.
If you want to see some of Ghislain's handiwork, check out SECXBRL.info.