XML 52 R38.htm IDEA: XBRL DOCUMENT v3.10.0.1
Income taxes (Details) - USD ($)
$ in Millions
9 Months Ended 12 Months Ended
Sep. 30, 2018
Sep. 30, 2017
Dec. 31, 2017
Income taxes [Abstract]      
Effective annual tax rate 26.00% 32.00%  
Federal corporate tax rate 21.00%   35.00%
Discrete tax benefit $ 8.7 $ 3.3