XML 82 R81.htm IDEA: XBRL DOCUMENT v3.20.1
Shareholders' equity - At-the-market equity offering (Details) - USD ($)
$ / shares in Units, $ in Millions
 3 Months Ended 12 Months Ended
Jul. 19, 2019
Sep. 30, 2019
Dec. 31, 2019
Shareholders' equity      
Maximum value of shares that can be issued from treasury to public 200,000,000    
Average price per common share   $ 96.56  
Gross proceeds from share issues   $ 138.4  
Net proceeds from share issues   136.0  
Share issuance agent commission costs   1.4  
Share issue costs and expense   $ 1.0  
Share Capital (Note 19)      
Shareholders' equity      
Number of shares issued at At-the-market equity offering     1,433,400