Do I still get the ';Campaign Complete: Legendary Achievement'; if I do half lvls alone, and half co-op?

Lets say I beat the first 5 levels on Single Player and got the achievements for those, and then did the rest of the levels on Co-Op, and get the achievements for those, do I still get the ';Campaign Complete: Legendary (or whatever difficulty I did) Achievement'; even if I didn't do the whole game by myself, or all with a friend?Do I still get the ';Campaign Complete: Legendary Achievement'; if I do half lvls alone, and half co-op?
Yes, you should still get the achievement. Also, I'm pretty sure if you beat it on Legendary, you get the achievements for beating it on the lower difficulties as well.