css原生table添加滚动条后改变滚动条的大小后让thead与tbody 对齐

HTML:

<table class="layui-table cic-table">
   <thead>
       <tr>
           <td class="td-title"></td>
           <td class="td-title row-title"></td>
       </tr>
   </thead>
   <tbody>
       <tr>
           <td class="td-title"></td>
           <td class="first-title"></td>
       </tr>
   </tbody>
</table>

CSS：

.cic-table tbody {
   	max-height: 330px;
    display: block;
    overflow-y: auto;
}
.cic-table thead, .cic-table tbody tr {
    width: 100%;
    display: table;
    table-layout: fixed;
}
.cic-table thead {
    width: calc(100% - 3px); /*减去默认滚动条的宽度，让thead 与tbody 对齐*/
}
/*改变滚动条的宽度和样式*/
.cic-table tbody::-webkit-scrollbar { width: 3px;}
.cic-table tbody::-webkit-scrollbar { width: 3px;}
.cic-table tbody::-webkit-scrollbar-track{background-color:#f0f0f0;}
.cic-table tbody::-webkit-scrollbar-thumb{background-color:#CCCCCC;}
.cic-table tbody::-webkit-scrollbar-thumb:hover {background-color:#CCCCCC;}
.cic-table tbody::-webkit-scrollbar-thumb:active {background-color:#CCCCCC;}