v3.19.3.a.u2
Goodwill - Goodwill by reportable segment (Details) - USD ($)
$ in Millions
Dec. 31, 2019
Dec. 31, 2018
Dec. 31, 2017
Changes in the carrying amount of goodwill      
Goodwill $ 21.3 $ 21.3 $ 21.3
Curtis Palmer      
Changes in the carrying amount of goodwill      
Goodwill 14.4 14.4 14.4
Morris      
Changes in the carrying amount of goodwill      
Goodwill 3.3 3.3 3.3
Nipigon      
Changes in the carrying amount of goodwill      
Goodwill $ 3.6 $ 3.6 $ 3.6