If the idea is related to the subject or work of the current company then in court they can claim inception for your later similar work. This happened in the c

If the idea is related to the subject or work of the current company then in court they can claim inception for your later similar work. This happened in the case where an action figure designer left Mattel to produce new (and completely unrelated) action figures at home. In court Mattel claimed the inventor form the idea for the new concept while employed at Mattel and the court agreed so Mattel took position of the new idea. While the new idea was functionally different it wasn't novel enough to qualify as original apart from the inventors prior experience doing similar work. To be more safe I would wildly alter the idea so that it applies in different functional applications for industries the current employer has no interest in performing. Then, at the very least, they cannot claim violations of non-compete status and you have a wider field of novelty.