I joined a working group the other day and they set down a groundrule that I really liked. I'm going to change it because I like visual pictures, but hopefully not change the meaning at all.
Let's say you have an idea. It's like a hippo made of Play-doh. When you're ready to share, you place it on the table, you step back and take your hands off of it. The other members of the group alo now own it. If they touch it, thier fingerprints will also appear in the clay -- you must really accept that this is no longer yours. If you're not yet ready to share it, keep it away from the table.
What's interesting in is is also what's not said. You really need to make sure that you have enough definition (communication, clarity, supporting detail) in your clay hippo to make sure the rest of the team understands it's a hippo. Otherwise, they might suggest adding big ears, tusks and a trunk. Or suggest the color is great, but that it ought to be a duffel bag.
Even more so, the whole idea that this is teamwork. Even if they pick it up, look it all over and announce that it's a fine hippo, again, their fingerprints are on it. This isn't a solo effort. Even a fully developed idea is going to be a group contribution, so don't think only your fingerprints are going to be on it.
And when it's finally presented to others, someone else might be the one showing it off.