How to Add Static Members in EcmaScript 5

I want to add a static function to a class in EcmaScript 5 JavaScript. My class definition looks as follows:

var Account = {};

Object.defineProperty(Account, 'id', {
    value : null
});

And I would create a new instance like this:

var theAccount = Object.create(Account);
theAccount.id = 123456;

Now I want to add a static function to the Account class. If I had created the Account class using a constructor function and the prototype property like this:

var Account = function () {
    this.id = null;
};

...I could just do:

Account.instances = {};

Account.createInstance = function () {
    var account = new Account();
    account.id = uuid.v4();
    Account.instances[account.id] = account;
    return account;
};

But since I am using Object.defineProperty and not the prototype property to add members, Account.instances and Account.createInstance would also be instantiated when calling Object.create and therefore be properties of the instance.

How do i add a static member to a class when using EcmaScript 5 style object creation?