Waiting for Big 4 offer

I had an interview at a Big 4 last week and after about an hour after the interview was called and told they were moving forward with me. We also talked a little about comp but I have not heard from them since. Anyone have any experience with a situation like this? How long does it typically take to get your official offer at a Big 4? Also, what is the background check process like? Anything would be helpful. Thanks.