css - bootstrap: form-control size doesnt change based on parent div col size -

i trying use increase size of text box changing col-md-* value doesn't seem affect child input form-control textbox.

example:

<form id="myform">     <div class="row">         <div class="col-md-2">             name:         </div>         <div class="col-md-8">             <input name="name" type="text" placeholder="enter name ..." class="form-control" required="required" />         </div>     </div> </form> 

in above code text input size doesn't increase think should larger if used col-md-8. text box size same whether use col-md-4 or col-md-6 also. because form-control class in bootstrap defines size? if how can fixed?

try work me

<div class="row">         <form id="myform">             <div class="col-md-2">                 name:             </div>             <div class="col-md-8">                 <input name="name" type="text" placeholder="enter name ..." class="form-control" required="required" />             </div>         </form>      </div>