Personally, I wouldn’t approach multiple companies at the same time for the same idea, because of one big reason. If a company is interested, the first thing they would do is ask 2 important questions: ‘what other company knows about your idea?’, and ‘do you have a patent or a PPA for it?’
Every other reason derives from this first one.
When you start discussing with a company, an NDA is required, in which you’re asked to disclose which companies you have already talked to about your idea. So if you show your idea to multiple companies you’re basically lowering your chances, you’re giving away your advantage. What you ideally want to do is make the companies think they have an advantage over their competitors, make them play off one another.
And lastly, something you shouldn’t even start approaching companies if you don’t have yet is a patent or at least a PPA. You have to be careful not to have your idea stolen. Don’t assume that if a company is huge it also has good ethics. That’s false in 90% of the cases. If we look back, history will show us many cases of corporations stealing ideas from regular people who could do nothing about it. Just like the inventor of the windshield wipers that are still used today, who got too excited and showed it to Ford Motor, and then watched his invention get successful under the name of someone else.