Question about encryption for emails with confidential attachments

Looking for some advice. I am thinking of signing up for a bank account with a financial institution that has no physical locations. They would like me to send documents (pictures of DL/Passport/etc) to verify my identity, by email. They say the email is encrypted but all I see is the usual TLS. I know nothing about encryption but have always gone by the rule that nothing like ID should be sent by email either in the body of the email or as an attachment. Is this a good rule to follow or is it safe to send these types of documents with TLS?