> I work with XBRL instance documents and frequently find the 
> following default namespace:
> xmlns="http://www.xbrl.org/2003/instance" 
> 
> I have been removing it for processing with XSLT/XPath/XQuery
> 
> Can anyone suggest  another solution?

Removing it isn't a solution, it's a hack.

In XSLT 1.0, to refer to an element in a namespace, your stylesheet needs to
bind a prefix to that namespace and you need to use a prefixed name to refer
to the element.

In XSLT 2.0, you can use xpath-default-namespace to declare the namespace
that unprefixed element names in your path expressions (and match patterns)
refer to.

Google for "XSLT default namespace" for a zillion other messages saying the
same thing.

Michael Kay
http://www.saxonica.com/