Improve checkin d4e04fc

Removal of unused list of modelObjects
Use of root.iter prevented clearing __dict__ of objects,
resulting in slow close of some instances.

arelle/ModelDocument.py

@@ -634,7 +634,8 @@ def close(self, visited=None, urlDocs=None):
             xmlDocument = self.xmlDocument
             dummyRootElement = self.parser.makeelement("{http://dummy}dummy") # may fail for streaming
             for modelObject in self.xmlRootElement.iter():
-                modelObject.clear() # clear children
+                modelObject.__dict__.clear() # clear python variables of modelObjects (not lxml)
+            self.xmlRootElement.clear() # clear entire lxml subtree
             self.parserLookupName.__dict__.clear()
             self.parserLookupClass.__dict__.clear()
             self.__dict__.clear() # dereference everything before clearing xml tree