An NDA protects the idea-generator, in cases like this. To get into detailed discussions, without protection, opens the inventor to potential prejudice.

I've always applied a simple rule to my own innovations:
If the client/interested party will not sign an NDA then they are either not serious about follow-through, or they are potential crooks - I then close the communication channel.

The first step should always be an NDA.

The times when I over-rode my rule & worked on trust, are the ones where I often came unstuck.