"cleared to Detroit as filed", you're cleared to Detroit, as he said. This is why in planning a flight, you should pick a way-point that's on a segment of an approach. When you file, your ETA is to the airport, including approach. Always how I have done it. When it comes to lost comms, remember these:
highest of Altitdude: M- Min altitude for IFR flight
E - Expected
A- Assigned
Route: by route Assigned
direct to vectored fixed
Expected
filed
So lets say you don't have a CL that is a fix from which an approach begins, and you have lost comms IN IMC. leave the CL at ETA and commence an approach from an approach fix that puts you at the airport. Usually your CL is the airport, so it works well.
If if is, go to the fix and hold until your ETA, and start approach.
Lets say we're holding over a fix and EFC at 1200. we hold over that fix until 1200, then go the route as the above says. That's why there is an EFC, in case of comm failure. So most of the time, the airport IS your clearance limit. Remember CRAFT? Cleared to (that's your CL)