A potential collaborator applies for a grant on his own: what should I do? In response to a solicitation in an area of my expertise, I approached a known expert in a different field; I had thought of a way to apply that field to solve the problem.  He liked my idea and set up a meeting with him and his postdocs; over time, we went through several rounds of written communication, proposal outlines, research plans, and revisions amongst us.

Midway through, I learned more about the solicitation and concluded that it wasn't a good match; we discussed this, decided not to apply, but that the plan was good and that we should look for other sources of funding.  As we did this, we continued to do some revisions together.

A while later, he sent me an email that he found a good source of funding, that he has a good relationship with the source and doesn't really need a partner for it, and that he is going to apply without me.  I was quite upset, but, seeing that he was telling me and not asking me, and that I had no way to stop him, said "okay, makes sense, please send me a copy of the proposal and keep me informed."

In truth, his proposal was advanced far beyond what I had last worked on.  But, the core idea was mine; and I have the records to attest to that, not to mention that his postdocs could verify that as well.

Assuming he gets the grant, I have no desire to get a share of the funds.  At this point, he can do the rest of the work without me.  He really is an expert and manages a very large, very prominent research program with lots of high profile funding.  And rightfully so - he produces results.

What I would like is coauthorship.  After all, the entire approach is my idea.  I thought of using his area of expertise to solve a very high profile problem of growing importance in my field, and described to him in detail why all the indigenous methods to my field are failing, and why an approach drawing on his expertise could succeed.

What is the right way to handle this? I won't be satisfied with an acknowledgement at the end; I'd like to be one of the authors.  I'm happy helping with the research further though I'm not sure he feels he needs me.

And, moreover, is this type of behavior acceptable? Do I have any leverage here? Do I need it?



CLARIFICATIONS: 


To clarify, while I certainly didn't do the research yet, it was more than just giving him an idea.  I sent an outline, discussed the plan, and spent hours revising and iterating on their research plan.  I'll be equally clear that the final proposal was very high quality, and went far beyond what I had worked on.
From the responses, it seems this falls into a grey area.  So let me revise my question: Given that he's probably going forward with this, what's the best way to approach him and ask to be a coauthor? I'd be happy being involved with the research itself, but I'm not sure he wants that.  He'd probably be best off career-wise keeping it to him and his students (and, mind you, this is a researcher who puts a lot of effort on career advancement - he's an equally talented businessperson, albeit in academic research, as scholar).
I am somewhat surprised about the answers so far. The behavior of the professor as described seems at least a little unethical at best, and downright exploitative at worst. If a more junior researcher comes to you with a good idea and some first steps towards a concrete research plan, and you answer with (basically) gee, good work, now please excuse me while I do this research with my own students, I have a hard time seeing how this would be in any way considered fair. Asking the OP to be happy because he "helped progress science" after all is ... ok, I have literally no good word for this expectation. As we all know, reputation is the currency of science, and it sounds like the OP was badly short-changed.

Whether the professor "needs" the OP or not is, to me, not really the important question here. The OP had the original idea, so it is unlikely to assume that he would be entirely useless in the remainder of the project. Hence, cutting him out of the research basically right from the start seems really awful. The least you can do is take him on and give him a chance to contribute to the research - if it then turns out that he or she actually lacks all the relevant knowledge to contribute from the project from then on (unlikely), you can still decide together to part ways later on.


  And, moreover, is this type of behavior acceptable? Do I have any leverage here? Do I need it?


I wouldn't consider it ethical at all. Whether you have any leverage is another question - likely no, as (as correctly noted above), just having the idea by itself does not warrant co-authorship (but you should have been given the chance to do more), but it is kind of too late for this now.


  I'd be happy being involved with the research itself, but I'm not sure he wants that. He'd probably be best off career-wise keeping it to him and his students (and, mind you, this is a researcher who puts a lot of effort on career advancement - he's an equally talented businessperson, albeit in academic research, as scholar).


As I said, it is a bit late to ask for co-authorship of a thing that's already been written without you. If you don't actually want to be involved in the rest of the project, I am not sure what you can realistically ask for. In this case, I am not sure if you can get much more than an acknowledgement that you brought the idea to the mind of the professor. 

(that being said, I wouldn't touch a collaboration with this guy anymore for the rest of my life)