That's fairly common in investment banking and is called "gardening leave". My understanding is that in banking you get your salary but not your bonus during the gardening leave period.
Usually (and I know this from personal experience) if you are senior enough you have a notice period of 3-6 months and under normal circumstances you are expected to do a proper handover before leaving. Sometimes they don't want you to come in to the office or have access to the corporate network/data but they still want access to you in case they need it.
Non-competes are usually 18-24 months and I don't think anyone is going to pay that for you to sit on your butt.