html:

<div class="detail">
    <div class="detail-wrapper">
        <div class="detail-main"></div>
    </div>
    <div class="detail-close">
        <span class="iconfont icon-guanbijiantou"></span>
    </div>
</div>

css:

.detail{
    position: fixed;
    top: 0;
    left: 0;
    z-index: 100;
    width: 100%;
    height: 100%;
    overflow: auto;
    background-color: rgba(7, 17, 27, .8);
}
.detail-wrapper{
    min-height: 100%;
}
.detail-main{
    margin-top: 64px;
    padding-bottom: 64px;
}
.detail-close{
    position: relative;
    width: 32px;
    height: 32px;
    margin: -64px auto 0 auto;
    clear: both;
    font-size: 32px;
}

sticky footer