.sidebar-header {
  background-color: #f5f5f5;
  border-bottom: 1px solid #e5e5e5;
  box-sizing: border-box;
  padding: 11px;
  position: absolute;
  width: 100%;
  z-index: 1;
}

.sidebar-header > .search-input {
  -webkit-appearance: none;
  border: 1px solid #ccc;
  border-radius: 3px;
  box-shadow: inset 0 1px 2px rgba(0, 0, 0, .075);
  color: inherit;
  font: inherit;
  font-size: 12px;
  height: 26px;
  outline: 0;
  padding: 1px 4px;
  width: 100%;
}

.sidebar-header > .search-input:focus {
  border-color: #51a7e8;
  box-shadow: 0 0 1px #51a7e8;
}

.sidebar-header > .search-input::-webkit-search-decoration {
  display: none;
}

.sidebar-header {
  background-color: #f5f5f5;
  border-bottom: 1px solid #e5e5e5;
  box-sizing: border-box;
  padding: 11px;
  position: absolute;
  width: 100%;
  z-index: 1;
}

.sidebar-header > .search-input {
  -webkit-appearance: none;
  border: 1px solid #ccc;
  border-radius: 3px;
  box-shadow: inset 0 1px 2px rgba(0, 0, 0, .075);
  box-sizing: border-box;
  color: inherit;
  font: inherit;
  font-size: 12px;
  height: 26px;
  outline: 0;
  padding: 1px 4px;
  width: 100%;
}

.sidebar-header > .search-input:focus {
  border-color: #51a7e8;
  box-shadow: 0 0 1px #51a7e8;
}

.sidebar-header > .search-input::-webkit-search-decoration {
  display: none;
}

Add 'box-sizing' of search-input for IE
Add 'box-sizing' of search-input for IE
