jQuery(document).ready(function(){
  
  var sidebar = jQuery("#Sidebar");
  var sidebar_default_position = sidebar.offset().top;
  var wpadmin_header_height = -1;
  var sidebar_top_margin = 20;

  jQuery(window).scroll(function(){
    
    if(wpadmin_header_height == -1){
      wpadmin_header_height = jQuery("#wpadminbar").length > 0 ? 28 : 0;
    }
    
    var scroll_position = jQuery(window).scrollTop();

    if( scroll_position - ((sidebar_default_position - wpadmin_header_height) - sidebar_top_margin) > 0){
      sidebar.css({position: "fixed", top: (sidebar_top_margin + wpadmin_header_height) + "px"});
    }else{
      sidebar.css({position: "relative", top: "0px"});    
    }

  });
  
});