Atlanta -3 is an early christmas gift. Atlanta is playing for home field advantage throughout the playoffs. if they win, the next away game they would play is in New Orleands for the SuperBowl, a stadium they are very familiar with.
Detroit is 4-8 and seem to find a way to lose every game. they have the #2 offense in the nfl passing but lets consider that they are always down so they pass a lot and they are always down by 21 points so they are trying to play comeback every game.
I would take Atlanta -6.5 in this game. I am not sure wha Vegas is thinking, but Atlanta brings it tonight, wins by 7+ points and plays at home through the playoffs.