Trending @Infosys; Waiting time for getting offer letter

I have selected in TCS by clearing technical round. On same day, HR told to submit documents for further process and she told that she verified all docs and now I have to wait patiently until other team contact me and give my offer letter. Today I marked 20 days in hope to get call from TCS team for offer letter. Is any one having any idea how much time I have to wait for offer letter after document verification?