Ideas are cheep though. It's execution that matters. The idea won't be worth anything if you don't get it in the hands of your customers. 100% of zero is zero.
If the idea is truly, really, honestly so amazing that anyone who heard the idea could beat you, then it sounds like the idea combined with your unique situation (skills + connections + prototype) isn't that great. Otherwise, what's stopping someone else from beating you?
I have an idea - faster than light travel! The idea is nothing without execution however...
I was incredibly concerned about this with an idea I had. A shared the 'idea' with a mentor of mine, who was 'well off' and not technical. This mentor agreed that before I involve other people I should speak with a lawyer to see how to best protect the idea because like you it seemed to be (and researched to be) an original concept.
He hooked me up with a lawyer and we discussed the options for copyright, patent, etc. Long story short the decision was that there wasn't a clear method of 'protecting' the idea due to it's complexity. I'm not saying you shouldn't consult a lawyer - there are certain things that are easier to trademark, copy, or patent. My idea is/was a biz to consumer saas if that helps any.
I didn't feel any better about sharing with others after that meeting - my mentor had reached out to his contacts who were more aligned with getting startups off the ground to as about what to do in this situation. What was explained to me was that what really matters is how fast you can go from zero -> 'minimum viable' (which could just be detailed ins and outs of all the pieces) -> poc -> 'market'
If there are high startup costs and you can't create a shotty demo or something, then sit down and write as detailed of a 'plan' as you can. Doesn't have to be a business plan, because depending on your expertise you may not care about monetizing it and can utilize people who can bring ideas to the table later on. What you're trying to do is document and plan out how it will work in as much detail as you can. Draw pictures, write process, write pseudo code, mock up layouts digitally if you can, basically whatever you possibly can get into a some kind of organized 'plan.'
While you're doing this it'd be smart to have an audit log that can be validated somehow. Pictures of you working on it where it's clearly visible, certified mail copies of it to yourself, whatever you can do to prove it was you who did this, and this is when it happened.
That's all I've got, I hope it helps. For what it's worth - the idea I'd come up with still doesn't exist for the most part out in the wild, and it has been roughly 4 years. The startup costs for me aren't high, it was the lack of knowledge to get it done myself that caused me to only do the planning bit I described above. My circle of people to tap at the time with the know how wasn't what it is now. (I got more into programming and it widened how many other programmers I know)
Perhaps someday I'll get going on a shotty demo of it to pitch ;)