how to add dynamic height to overlay in jquery dialog box

1function showDialog(title, content) {
2                var height = $(document).height();
3                $("#message").dialog({
4                    modal: true,
5                    width: "auto",
6                    position: {my: 'top', at: 'top'},
7                    buttons: {
8                        Ok: function () {
9                            $(this).dialog("close");
10                        }
11                    },
12                    open: function (event, ui) {
13                        $(".ui-dialog-titlebar-close", ui.dialog | ui).hide();
14                        $('.ui-widget-overlay').css('height',height);
15                    }
16                });
17            }