Bootstrap nested nav

HTML

<link rel="stylesheet" href="http://twitter.github.com/bootstrap/assets/css/bootstrap.css">
<script src="http://twitter.github.com/bootstrap/assets/js/jquery.js"></script>
<script src="http://twitter.github.com/bootstrap/assets/js/bootstrap-dropdown.js"></script>
<div class="container">
  <div class="row">
    <div class="col-sm-3">
      <ul id="drilldown" class="nav nav-pills nav-stacked">
        <li><a href="#">menu item 1</a></li>
        <li><a href="#">menu item 2</a></li>
        <li><a href="#" data-toggle="collapse" data-target="#drilldown-1">menu item 3</a>
          <div style="padding-left:0px;">
          <ul id="drilldown-1" class="nav nav-pills nav-stacked collapse">
            <li><a href="#">menu item 3-1</a></li>
            <li><a href="#">menu item 3-2</a></li>
            <li><a href="#">menu item 3-3</a></li>
          </ul>
          </div>
        </li>
        <li><a href="#" data-toggle="collapse" data-target="#drilldown-2">menu item 4</a>
          <div style="padding-left:0px;">
          <ul id="drilldown-2" class="nav nav-pills nav-stacked collapse">
            <li><a href="#">menu item 4-1</a></li>
            <li><a href="#">menu item 4-2</a></li>
            <li><a href="#">menu item 4-3</a></li>
          </ul>
          </div>'
        </li>
        <li><a href="#">menu item 5</a></li>
        
      </ul>
    </div>
  </div>
</div>

CSS

.nav li.dropdown ul.dropdown-menu li.nav-list:hover {
    background: #08c;
    color: #fff;
    cursor: pointer;    
}

.nav li.dropdown ul.dropdown-menu .nav-list {
    font-size: 13px;
    color: #333;
    float: none;
    line-height: 21px;
}

.nav li.dropdown ul.dropdown-menu li:hover ul {
    display:block;
    position:absolute;
    left:100%;
    -webkit-border-radius: 3px;
    -moz-border-radius: 3px;
    border-radius: 3px;
}

.nav li.dropdown ul.dropdown-menu ul {
    display: none;
    float:right;
    position: relative;
    top: auto;
    margin-top: -27px;
}

.nav li.dropdown ul.dropdown-menu .nav-list .caret {
    border-bottom-color: #999;
    border-top-color: #999;
    float: right;
}

.nav li.dropdown ul.dropdown-menu .nav-list:hover .caret {
    margin-left: 6px;
    margin-top: 5px;
    margin-right: 1px;
    border-right: 0;
    border-left: 4px solid #fff;
    border-top: 4px solid transparent;
    border-bottom: 4px solid transparent;
}

.nav li.dropdown ul .nav-list .dropdown-menu:after {
    top: 8px;
    left: -12px;
    border-top: 6px solid transparent;
    border-bottom: 6px solid transparent;
    border-right: 6px solid #fff;
}

.nav li.dropdown ul .nav-list .dropdown-menu:before {
    left: -7px;
    border-left: 0;
    top: 7px;
    border-top: 7px solid transparent;
    border-bottom: 7px solid transparent;
    border-right: 7px solid rgba(0,0,0,0.05);
}