$250k per account, up to 6 accounts. So the FDIC insures up to $1.5 million. If you have more then that, I think you can find other ways to secure your money.
Anything above FDIC insurance limits and you’re in US Treasuries, backed by the full faith and credit of the US Treasury. They’re one of the safest financial assets in the world. The risk of default is almost, but not quite, zero.