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CAPITAL DISCLOSURES (Details)
$ / shares in Units, $ in Millions
12 Months Ended
Feb. 21, 2018
USD ($)
$ / shares
Dec. 31, 2017
USD ($)
$ / shares
Disclosure of objectives, policies and processes for managing capital [line items]    
Net debt leverage ratio   1.0
Dividends paid | $   $ 84.8
Dividends declared per common share (in dollars per share) | $ / shares   $ 0.374
Dividends declared before financial statements authorised for issue but not recognised as distribution to owners, percentage increase 20.00%  
Dividends declared before financial statements authorised for issue but not recognised as distribution to owners (in dollars per share) | $ / shares $ 0.112  
Dividends declared before financial statements authorised for issue but not recognised as distribution to owners | $ $ 24.6  
Minimum    
Disclosure of objectives, policies and processes for managing capital [line items]    
Target net debt leverage ratio   1
Maximum    
Disclosure of objectives, policies and processes for managing capital [line items]    
Target net debt leverage ratio   2