How to give Style for Html helper CompleteEditorFor ?

MVC View

<%: Html.CompleteEditorFor(m => m.Quantity, labelOverride: "Quantity In")%>

Style 

<style type="text/css">

        #Quantity
        {
            width: 100px !important;
        }

    </style>

Note: Be aware that Auto generated id value for html controller is Case Sensitive (ie: Quantity)
           Inside the style I have used !important property for override any existing width property
           inherit from other classes.