I have limited knowledge of the IAE engines however on the CFM models leaks of oil and or fuel can be common. This is most likely to occur after an extended shut down period or overnight. I have had to motor an engine on several occasions prior to push back to ensure the leak has stopped.
Maintenance has several theories on CFM leaks. Our fleet is mixed and we have some IAE but I have not flown that version. Some Maintenance techs are of the opinion that they observe more leaks in windy conditions. If the aircraft is parked with its tail to the wind the fans spin backwards. The theory is that there may be some very slow movement of the inner spool which causes the seals to lie the wrong way. They are cold and less pliable. This is especially noticeable in the winter. Once the engine is started the seals are aligned properly and the tighten up and the leaking stops.
In your situation it may be that the IDG was over-serviced. It is a normal overnight maintenance check at a lot of carriers and sometimes the IDG oil filler neck is not easy to get to or it is easy to over-service. The old Prat's were very sensitive to CSD overfills.
I can attest however that both IAE and CFM use a leak rate check after the engine has been run of determine if the engine and aircraft are able to be dispatched. That is the only maintenance action required.