QuoteI've built a document where I explain everything about it: any functionality and gameplay. I've finished the project and all the design
It's a common mantra that ideas do not have much value. The implementation of the design is what is valuable. The exception to this rule is if your design document includes every micro-detail including the programming implementation, database structure, and art assets. So why don't you share a synopsis of your project such as what would be shared on a crowd-sourcing platform?
On topic, you can form a company and sell stocks to investors, but it seems impossible for you to acquire a million USD. Facebook was made by one person, so why can't you also create the entire project with place holder assets until you convince investors to fund the project? You said you already finished the project and all the design, but I am not sure exactly what you mean.