There's lots of useless replies in here so far, and some half-baked ones. First, determine whether you have an intellectual property assignment for this idea. This could be determined by local laws, a contract you signed, and the manner in which the idea was created an implemented.
Many companies and jurisdictions don't have an explicit intellectual property assignment. Let's assume that's the case. Let's also assume that you came up with the idea outside of working hours, and utilized your own software, equipment, internet connection, etc to build this thing.
Next, consider whether or not this invention of yours is applicable to others in the same industry, or different industries that need to accomplish a similar task. If that's the case, then you might have something valuable.
If you have something valuable, you might want to look into filing a patent. When you file the patent, and if it gets approved (can take years), you now have exclusive rights to the invention. Patents in software are more how the 'process' than the actual code itself. EG: "use computer software to take values from data source X, do something useful here, output results to Y."
You should consult with a patent attorney if you think it's really valuable. You'll need to perform some research to determine if the invention is already patented.
Now, once you've applied for the patent, and you believe that you don't have an intellectual property assignment favoring your employer for it, would be the time to offer to demonstrate the software. The software should not be present on company machines, etc. You probably want to work out the exact steps with your patent attorney on the protocol here.
Even though it make take years to be awarded the patent, if the patent is found valid, then you'll have coverage from the time of filing, at least in the US. This means if the company steals your idea and implements it themselves, they've stolen your patent, and would be liable for damages. What I think the best outcome is you agree to license the product to the company for $X/yr.
Now, all that's a heavy handed approach and might lead to litigation, so consider your best options carefully.
If you decide the above is too much, or the invention is not that valuable, or you think it's not worth the trouble, I would bring it up to management that you have an idea to solve the problem, but don't mention you have the solution. Negotiate a bonus, promotion, or raise for the implementation. Unfortunately for you, they can just decide to make you work on it during the course of your normal day, and you'll get nothing.