XBRL International held a webinar which explained the UML model they are creating for XBRL, referred to as the XBRL Abstract Model. You can watch this 1 hour 34 minute video on YouTube here.
For those serious about understanding XBRL, this video is worth investing in. As stated in the webinar, XBRL International is trying to create two models:
One of the most useful aspects of this video are the very, very good questions which were asked. The webinar stated that a public working draft of this model would perhaps be available in October.
The semantic model which I have created can be found here. My model, which would fit into the model I saw in the webinar, is more focused on financial reporting and tends to be at a higher level than the model created by XBRL International.