The latest issue of the Journal of Accountancy contained an article showing step by step how to markup a financial statement in XBRL using Rivet Software's Dragon Tag product. Click here to see the article: http://www.aicpa.org/pubs/jofa/feb2008/six_steps.htm
I don't think it's going to be as difficult or costly as a lot of people think. Obviously there will be a learning curve but nothing as painful or costly as Sarbanes Oxley.