Some time ago I used JAD (JAva Decompiler) to achieve this - I do not think IntelliJ's decompiler was incorporated with exporting in mind. It is more of a tool to help look through classes where sources are not available.
JAD is still available for download, but I do not think anyone maintains it anymore: http://varaneckas.com/jad/
There were numerous plugins for it, namely Jadclipse (you guessed it, a way to use JAD in Eclipse - see decompiled classes where code is not available :)).