public function setAccountId($accountId)
    {
        $accountId = (int) $accountId;

        if ($this->accountId < 0) {
            throw new \UnderflowException('Value of "accountId" must be greater than 0');
        }


        if ($this->exists() && $this->accountId !== $accountId) {
            $this->updated['accountId'] = true;
        }

        $this->accountId = $accountId;

        return $this;
    }