How to allow smooth scrolling in all browsers

I have recently noticed that when you have a div containing overflowed content that is scrollable, in chrome, you can smoothly transition scrolling from that div to the rest of the body, but in Safari, you can not. Instead of smoothly transitioning, the scrolling stops when you reach the top or bottom of the contained element, and you must scroll again to begin scrolling on the body. It is vital to the project I am working on that I allow Safari to scroll smoothly the same way Chrome does. For the life of me I can not figure out how to do this. Any input is appreciated, thank you for your time!