When a member of your Google Apps Domain leaves and needs to have their Google Docs transferred, it is easy to reassign ownership of their docs (but you have to be the Google domain Admin or have admin-equivalent rights):
1. Log into the control panel and select the Advanced Tools tab
2. Navigate to near the end of the Advanced Options and add the From: and To: addresses and press the "Transfer Documents" button:
The "From:" user still has view and edit access but is now no longer the owner. Done!