There are two potential routes.
Cheap way: bring your invention idea to many companies with a business plan of how it can help their business. If you are lucky, you'll get a taker and you can negotiate a price for your idea. If you are normal, you'll get nothing but you'll lose nothing. If you are unlucky, you'll get interested parties that'll steal your invention and sell it as their own and you lose it all.
Expensive way: get a couple of patents (a picket fence type of defense). Even if one patent is lost (about half of all patents are thrown out in court), you still have multiple patents protecting your idea. Think roughly $15,000 per patent possibly quite more. That money is just for the US, if you want worldwide protections expect $50,000+ per patent. Then with your patented invention that cannot be stolen easilly, follow the cheap way above.
Remember, 90% of patented ideas go nowhere. Of that, 50% are thrown out in court. So expect a 5% success rate if you have a good idea.