Comment by GeekyBear

To be a bit more clear:

They offer standard encryption by default, where they hold a copy of your encryption key and can assist you if you lose access to your key.

They also allow you to opt into advanced data protection, where they do not have a copy of your encryption key, so you need to be sure you protect it yourself.

If a company has a copy of the customer's encryption key on their server, you have no choice but to hand it over in response to a warrant, as we recently saw with Microsoft handing over the bitlocker key for a customer's computer.