//Adds Custom Column To Users List Table
function custom_add_user_id_column($columns) {
    $columns['user_id'] = 'User ID';
    return $columns;
}
add_filter('manage_users_columns', 'custom_add_user_id_column');
//Adds Content To The Custom Added Column
function custom_show_user_id_column_content($value, $column_name, $user_id) {
    $user = get_userdata( $user_id );
	if ( 'user_id' == $column_name )
		return $user_id;
    return $value;
}
add_filter('manage_users_custom_column',  'custom_show_user_id_column_content', 10, 3);