Immigrant Visa - after interview

Hi Sajha folks, Wanted to know from your experience on how long does it take after the immigrant visa is approved during the interview for them to return the passport/documents? I heard some bank like Investment bank handles that process and can take up to 2-3 weeks but in embassy related website, it says, passport will be returned in few days. I was hoping to bring my spouse as soon as they hand back her passport and was hoping it to be like 2-4 business days and not 2-3 weeks.