title: Pandas - Filter multi-index by condition on all values within index
body: <p>I am trying to filter a dataframe with a multi-index similar to the following.</p>
  
  <pre><code>import numpy as np
  import pandas as pd
  
  data = pd.DataFrame(np.random.rand(8),
               index=[list('AABBCCDD'),
                      ['M', 'F']*4])
  data['Count'] = [1,2,15,17,8,12,11,20]
  </code></pre>
  
  <p>I would like to select all rows where 'Count' for <em>both</em> 'M' and 'F' inside a given outer level index is greater than 10. So for the example dataframe, all 'B' and 'D' rows should be selected, but none of the other rows. The only way I can think to do this is by looping through the outer index, but as loops in pandas are almost never the best way to do things I'm thinking there must be a better solution.</p>