cool-headed vs detached

cool-headed

adj
  • Calm and imperturbable, especially under pressure. 

detached

adj
  • Having or showing no bias or emotional involvement; disinterested. 

  • Not physically attached; separated from something it could connect to. 

  • Not influenced by anyone else; characterized by an impersonal objectivity; impartial. 

  • Of a house: not joined to another house on either side. 

How often have the words cool-headed and detached occurred in a corpus of books? (source: Google Ngram Viewer )