title: sum of 'float64' column type in pandas return float instead of numpy.float64
body: <p>I have a dataframe in pandas. I am taking sum of a column of a dataframe as:</p>
  
  <pre><code>x = data['col1'].sum(axis=0)
  print(type(x))
  </code></pre>
  
  <p>I have checked that <code>col1</code> column in <code>data</code> dataframe is of type <code>float64</code>. But the type of <code>x</code> is <code>&lt;class 'float'&gt;</code>. I was expecting the type of <code>x</code> to be <code>numpy.float64</code>.</p>
  
  <p>What is it that I am missing here?</p>
  
  <p>pandas version - '0.18.0', numpy version - '1.10.4', python version - 3.5.2</p>