External documentation is not available for the Angular APIs. Please follow this issue for updates: https://youtrack.jetbrains.com/issue/WEB-26406 But when external documentation is available, you can go to it by pressing Shift-F1 or using that button (it then becomes enabled).
Just to make sure we are on the same page here:Go to External Documentation opens documentation in the browser.If you are talking about method descriptions in the doc popup, these descriptions are extracted from the d.ts files and for Renderer there are not available descriptions