An insurance company, like Hugh Woods, won't insure your collection unless it is in a secure location, including a bank safety deposit vault, or in a modern, proper safe stored within a home in a secure location away from possible water damage areas such as a basement. These are part of the restrictions, including a proper evaluation by a compentent person such as a dealer. These are just some of the restrictions, lack also include a deductible of at least $500.
As others have mentioned, keeping notes in a Safety Deposit box at your bank is possibly the safest place to keep it.
Yes, indeed, banks get robbed and banks can have fire/smoke damage, however, this is rare.
Good photos of the notes with good recording of serial numbers and invoices kept together is an excellent idea. Remember, that to most insurance companies, banknotes have face value, thus the need to go to a company that specializes in collectables.
Rick