Show DIV based on onSelect event handler

I'm trying to show and hide DIVs based on the onSelect event handler, but it's not working.

This is my javascript:

function showDiv(divID) {
document.getElementById(divID).style.display = 'block';
}

And this is my HTML:

Type of payment account:
      <select name="paymentAccountType" onchange="showDiv(this);" >
      <option></option>
      <option>Credit card</option>
      <option>Debit card</option>
      <option>EFT</option>
      </select>

<div id="EFT" style="display:none;">EFT</div>
<div id="credit" style="display:none;">Credit card</div>
<div id="debit" style="display:none;">Debit card</div>