Detroit only has 1 game left and its against the Packers. Both teams are 11-4 and tied with the Cowboys. Winner of their game wins the North and finishes at 12-4. Both teams have the tiebreaker over Dallas which is conference record. Detroit 9-2, GB, 8-3, Dallas 7-4 against the NFC.
Assuming Arizona loses both games(they are down 21-6 right now and have San Fran next week) and Dallas wins next week, the Detroit/GB winner would be the 1 seed and Dallas #2