The idea is that you get a summary in the intellisense tooltip, and can press F1 to show the full help, or F12 to jump to the declaration (which usually includes the documentation).
I find I usually only need to read the full documentation once or twice and then the tooltips give me enough information to go on. Also, when I find myself needing the full documentation, I usually need to browse further (e.g. investigate the whole class and other methods). I can understand you wanting to see all the information, although I must say I personally prefer it the way it is.
I suspect if you actually had what you're asking for you might want to turn it off (or at least down) after a few weeks when it keeps taking over your whole screen to tell you stuff you already know about methods you type 20 times a day. That's probably why there aren't any tools out there to do it already.
If it helps, tools like Resharper give "better" intellisense tooltips. (I say "better" in quotes because I find Resharper gives me too much information, and the default Visual Studio approach of just showing me one overload at a time is actually a lot less 'in your face'. Many people like to have all this information at their fingertips though). The resharper tooltips still won't get you to a full copy of the documentation page though.