.content .mceNonEditable.embeditem {
    position: relative;
    overflow: hidden;
    width: 100%;
    padding-top: 56.25%;
}


    .content .mceNonEditable.embeditem iframe {
        position: absolute;
        top: 0;
        left: 0;
        bottom: 0;
        right: 0;
        width: 100%;
        height: 100%;
    }