There have been a number of reports recently (example) that gave rise to the perception that the UK FSA "ditched XBRL" in the context of its new Mandatory Electronic Reporting (MER), and that this was new news. Given the FSA's weight as a leading European financial regulator, this would appear like a major setback to XBRL's global momentum.
However, this perception needs to be qualified. A recent FSA statement maintains that the stated position is a simple reïteration of a policy established earlier, hence the reports are repackaged old news. The FSA continues to develop its MER system using XML, which can be described as a related, but more generic file format version of XBRL. A later migration from XML to XBRL is thus by no means precluded, especially seeing the FSA's main concern that there is not "sufficient XBRL experience within the UK currently to develop this system without incurring additional cost and risk". This assessment is transient by nature.
That being said, it appears unfortunate that the FSA backtracks behind its 2004 committment to XBRL, namely to develop and publish an XBRL taxonomy. This would be a more appropriate way going forward, rather than deploying a mature technology in a newly implemented financial market infrastructure project, with which the FSA could play the rôle of an essential catalyst.