Get Parent ID while calling termSet.getAllTerms() using SP.Taxonomy.js

I am using the termSet.getAllTerms() method from SP.Taxonomy.js. I am able to get the term's ID, Name, childTermCount, isRoot and so on. But I need to get the ID of the Parent term, without making additional call to executeQueryAsync. Can anyone please tell me how to get it? I tried with term.get_Parent() and then parent.get_id(), but it throws the exception saying Property not initialized. Even though, I am able to get the Parent, I am unable to get its ID, without making another call.