table.quantiles {
    margin: auto;
    margin-bottom: 1.5em;
    font-family: serif;
}

table.quantiles th,
table.quantiles td {
    border: 1px solid black;
    padding: 5px;
}

table.quantiles th:first-child,
table.quantiles td:first-child {
    border-right: 3px double black;
}