Fixed TABLE header with scrollable tbody

HTML

<table class="fixed">
    <thead>
        <tr>
            <td>Name</td>
            <td>phone</td>
        </tr>
    </thead>
    <tbody>
        <tr>
            <td>AAAA</td>
            <td>323232</td>
        </tr>
        <tr>
            <td>BBBBB</td>
            <td>323232</td>
        </tr>
        <tr>
            <td>CCCCC</td>
            <td>3435656</td>
        </tr>
      <tr>
            <td>AAAA</td>
            <td>323232</td>
        </tr>
        <tr>
            <td>BBBBB</td>
            <td>323232</td>
        </tr>
        <tr>
            <td>CCCCC</td>
            <td>3435656</td>
        </tr>
        <tr>
            <td>AAAA</td>
            <td>323232</td>
        </tr>
        <tr>
            <td>BBBBB</td>
            <td>323232</td>
        </tr>
        <tr>
            <td>CCCCC</td>
            <td>3435656</td>
        </tr>
        <tr>
            <td>AAAA</td>
            <td>323232</td>
        </tr>
        <tr>
            <td>BBBBB</td>
            <td>323232</td>
        </tr>
        <tr>
            <td>CCCCC</td>
            <td>3435656</td>
        </tr>
    </tbody>
</table>

CSS

.fixed {
  width:350px;
  table-layout: fixed;
  border-collapse: collapse;
}
.fixed th {
  text-decoration: underline;
}
.fixed th,
.fixed td {
  padding: 5px;
  text-align: left;
  min-width: 200px;
}


.fixed thead {
  background-color: #333333;
  color: #fdfdfd;
}
.fixed thead tr {
  display: block;
  position: relative;
}
.fixed tbody {
  display: block;
  overflow: auto;
  width: 100%;
  height: 300px;
  overflow-y: scroll;
    overflow-x: hidden;
}
.fixed tbody tr:nth-child(even) {
  background-color: #dddddd;
}