.panel-group .panel-heading a {
  display: block;
  position: relative;
}
.panel-group .panel-heading a:after {
  content: '-';
  position: absolute;
  right: 20px;
  top:-11px;
  font-size:30px;
color: #999999;
}
.panel-group .panel-heading a.collapsed:after {
  content: '+';
color: #999999;
}