Why are they called the Detroit Partnership?

I'm just curious why the Detroit family are nicknamed the Detroit Partnership.

These guys seems to be really quiet compared to the other Cosa Nostra families in terms of busts and media attention.

Here is their lineup:

Detroit Partnership:

40 made members

100 associates

Boss: Jack "Jackie the Kid" Giacalone

Street Boss: Peter "Blackie" Tocco

Underboss: Anthony "Chicago Tony" La Piana

Consigliere: Anthony "Tony Pal" Palazzolo

Capos:

Joseph "Joey Jack" Giacalone

Joseph "Joe the Hood" D'Anna

David "Davey the Doughnut" Aceto

Paul "Big Paulie" Corrado

It's called the Partnership and the Combination because when it was formed in the early 30's it was a kind of merger of various gangs like the Eastside Gang for example run by Tocco and Zerilli, the Westside Mob and the River Gang run by the Licavollis.

It started as a partnership between the Toccos and Zerillis.
Sometimes they also refered to it as the Detroit outfit.

Thanks for your answers guys.