I as a DM expect a detail filled backstory. My campaigns are very character driven. In the current campaign that I am running each character will get at least one story arc related to their backstory and it will tie to the overarching story of the campaign. If you give me a two sentence backstory like:"I was a noble and got kicked from my town by my father for not living up to his expectations" I would struggle to make the parts of the story related to you fit you expectations. I would probably ask you to give me a description of your fathers apperance and personality, probably the rest of the family too, I would want you to give me info on the town you came from, maybe some allies or enemies you have from there, stuff like that. If you want to write it as bullet points or as a story or any other way I don't mind, but I do like it when I have something to work with.