Codeplex (and Gepsio) user jwokelly recently filed a bug noting that the Gepsio Nov 2011 CTP was failing to parse the XBRL documents created by Amazon to report their financial information for Q1 2012. More specifically, Gepsio was throwing a NullReferenceException while attempting to perform equality comparisons in the qualified name code.
I have just fixed this bug and have checked in a fix. The fix will be available in the next release (currently planned for Jul 2012). If you want to grab the code ahead of time, feel free to grab the latest source code here.
Many thanks to jwokelly for reporting a bug and for sending along the offending documents in a ZIP file. Gepsio now includes a unit test that parses these documents and ensures that no exceptions are thrown.