title: cannot convert nan to int (but there are no nans)
body: <p>I have a dataframe with a column of floats that I want to convert to int:</p>
  
  <pre><code>&gt; df['VEHICLE_ID'].head()
  0    8659366.0
  1    8659368.0
  2    8652175.0
  3    8652174.0
  4    8651488.0
  </code></pre>
  
  <p>In theory I should just be able to use:</p>
  
  <pre><code>&gt; df['VEHICLE_ID'] = df['VEHICLE_ID'].astype(int)
  </code></pre>
  
  <p>But I get:</p>
  
  <pre><code>Output: ValueError: Cannot convert NA to integer
  </code></pre>
  
  <p>But I am pretty sure that there are no NaNs in this series:</p>
  
  <pre><code>&gt; df['VEHICLE_ID'].fillna(999,inplace=True)
  &gt; df[df['VEHICLE_ID'] == 999]
  &gt; Output: Empty DataFrame
  Columns: [VEHICLE_ID]
  Index: []
  </code></pre>
  
  <p>What's going on?</p>