Where do rich people invest in stocks?

The question is in regard to ULTRA rich people, if you have say, $500M, where would you go to invest that safely?

If you put some in the bank, $250k is insured PER account, so you can stash a good few million away in bank accounts safely, but when investing in shares, is there any protection/law that saves you if your stock broker collapsed?

E.g, if you had $100m worth of stocks in interactive brokers or TD ameritrade accounts and they went broke, would your shares be safe to transfer elsewhere or what would be the process of action in this event?

Thanks!