XF 2.1 How do we change the editor default font size?

[Bimble]

We've changed the default post size and want to increase the editor font size to match - how do we change the editor font size in XF 2.1 please?

 

[Bimble]

This seems to work - please correct it if it's wrong (or affects other areas of the layout):

.fr-box.fr-basic .fr-element {
    font-size: 17px;
}