CSS how to push text away from border

The margin is outside of the border (see image below, it’s from the Chrome Developer Tools. The blue is the content of the element, the padding is the inside space of the element, the yellow is the border and the margin is the outside space of the element. Notice that there is a black box around border, that’s the edge of the element itself, the margin is additional space on the outside.

el-padding-border-margin

aside {
    width: 260px;
    float: right;
    border-top: 1px solid #21a1e1;
    border-left: 1px solid #21a1e1;
    border-right: 1px solid #21a1e1;
    border-bottom: 1px solid #21a1e1;
    padding-left: 0px;
    margin-left: 20px; // Add here
}