document.addEventListener("DOMContentLoaded", function(){
    document.getElementById('swap_type').
        addEventListener('change',
                         function(){
                             if(this.value=='CD_INDEX_TRANCHE'){
                                 document.getElementById('attach').parentNode.parentNode.style.display='block';
                                 document.getElementById('detach').parentNode.parentNode.style.display='block';
                             }else{
                                 document.getElementById('attach').parentNode.parentNode.style.display='none';
                                 document.getElementById('detach').parentNode.parentNode.style.display='none';
                             }
                         });
    var event = new Event('change');
    document.getElementById('swap_type').dispatchEvent(event);
})