How to change width of a pop-up or modal

If you want to change the width of your modal or pop-up for when you use your details page as pop-up use this code in the CSS tab of your modal/pop-up page:

.modal-dialog, .modal-body .x-type-row-container{
width: 1500px;

Set the width to the width you require, I used 1500 px here

Thanks for the tip @ashnil