Hovering over links in sidebar - I want WHOLE background to change, not just text.

I'm trying to make it so that when you hover over a link in a sidebar widget, it changes the background of the entire <li> area where that link is as opposed to just the text of that link.

For example, I'm trying to do what they did in the right sidebar ("popular articles") here: http://www.copyblogger.com/

The whole area around the text is highlighted when you hover over a link. In my case, just the text itself is being highlighted when it's hovered over.

How do I make that happen?

I'm currently (and unsuccessfully) doing this:

#right ul li a:hover {
background: #f0f0f0;
}