diff --git a/jedi/api.py b/jedi/api.py
index ab2af7d0..f0996fc5 100644
--- a/jedi/api.py
+++ b/jedi/api.py
@@ -74,14 +74,9 @@ class Completion(object):
     def doc(self):
         """ Return a document string for this completion object. """
         try:
-            parent = self.name.parent()
-            try:
-                return '%s\n\n%s' % (parent.get_call_signature(),
-                                     parent.docstr)
-            except AttributeError:
-                return str(parent.docstr)
+            return self.name.parent().doc
         except AttributeError:
-            return ''
+            return self.raw_doc
 
     @property
     def raw_doc(self):
diff --git a/jedi/parsing.py b/jedi/parsing.py
index dfb6212e..ad7dfe1b 100644
--- a/jedi/parsing.py
+++ b/jedi/parsing.py
@@ -410,6 +410,11 @@ class Function(Scope):
         lines[-1] += ')'
         return '\n'.join(lines)
 
+    @property
+    def doc(self):
+        """ Return a document string including call signature. """
+        return '%s\n\n%s' % (self.get_call_signature(), self.docstr)
+
 
 class Flow(Scope):
     """