What you want to do is check what flights from DTW to ORF there are after your scheduled flight, so that you know your options if you misconnect. Since your flights are in the morning, there should be a number of options, though some flights may be full.

If you do misconnect, Northwest will likely prefer to put you on its own flights (which are probably the only nonstop ones available) or Delta flights (which would involve a connection, probably through ATL). But be aware of what other airlines offer, in case all of the Northwest and Delta options that day are full.