public function isValid()
    {
        if(empty($this->token) || empty($this->payerId) || is_null($this->_paymentDetails)) {
            return false;
        }

        $valid = true;
        foreach($this->_paymentDetails as $detail) {
            if(empty($detail)) {
                $valid = false;
                break;
            }

            $amt = $detail->getAmt();

            if(empty($amt)) {
                $valid = false;
                break;
            }
        }

        return $valid;
    }