JQuery :: Replace All Text In HTML Containing Hello

I want to replace all text in the html that contains the word "Hello" to "Hi" (quotes not included and not case-sensitive). Here's what I've made:
if ($('body:contains("Hello")').length > 0) {
$("*").each(function () {
$('body').html($('body').html().replace('Hello','Hi'));
});}

Without the:
$("*").each(function () {
It only searches for the first word so I added the line above to search within all elements (If this is correct). But the problem is, I notice that the line I added seems to cause the page to run slower than usual. Is there any other way to do this?