v3.20.2
Income taxes - Other (Details) - USD ($)
$ in Millions
3 Months Ended 9 Months Ended
Sep. 30, 2020
Sep. 30, 2019
Sep. 30, 2020
Sep. 30, 2019
Reconciliation of income taxes        
Enacted statutory income tax rate 27.00% 27.00% 27.00% 27.00%
Tax expense $ 2.5 $ 0.2 $ 5.2 $ 2.4
Computed income tax (benefit) expense at Canadian statutory rate 5.5 3.9 11.5 5.9
Impact related to change in estimates     2.7  
Other permanent differences   0.2 0.9 0.7
Impact related to withholding federal and state taxes 1.1 0.5 1.7 1.3
Valuation allowance 133.8   133.8  
Increase (decrease) in the valuation allowance (2.7) (4.4) (11.6) (4.5)
Foreign exchange 1.4     1.0
Canada        
Reconciliation of income taxes        
Increase (decrease) in the valuation allowance 0.2 (1.0) (3.6) 4.4
United States        
Reconciliation of income taxes        
Increase (decrease) in the valuation allowance $ (2.9) $ (3.4) $ (8.0) $ (8.9)