I work for a AAA game company. Let me tell you something about a game developer/publisher that owns AAA IPs. They don't need “new ideas". They have enough ideas from their existing IP. They have planned their production all the way to 2019 (yup, it's very common for a AAA developer to plan 3–4 years, at least 2 games ahead). Ubisoft just released Assassin's Creed Syndicate last November, I bet they're already half way through the production of the next AC game, and probably already start the concept development of the AC game after the next.

If they want new IP, they would one) look for successful existing IPs (from movie, popular novel, TV shows, comic books…); two) look from within the company (game ideas from veteran developers, game designers.

And most importantly, a AAA game developer DO NOT WORK FOR HIRE. They hire remote developers  or work with outsourcing companies and contractors to support internal core team.

You have a good game idea? So has every single person in the game industry, from the summer intern to studio head to everyone in between. Idea is about the most worthless thing in the gaming industry.

Even if you have insane amount of money to purchase an existing AAA developer like Ubi Montreal, Treyarch, Bioware, Bathesda, Rockstar, or Riot, they'll still be working on their existing IP, Ubi Montreal will continue working on Assassin's Creed, and Far Cry; Treyarch will continue working on Call of Duty Black Ops; Bioware will continue working on Mass Effect and Dragon Age; Bethasda will continue working on Dishonored and Fallout; Rockstar will continue working on GTA and Red Dead; Riot will continue working on League of Legends.. so on and so forth.

So, your best bet is to create your own company. It has been done before. see: aspired. That didn't end very well… but maybe you can make it work.