v3.4.0.3
Income taxes (Details) - USD ($)
$ in Millions
3 Months Ended
Mar. 31, 2016
Mar. 31, 2015
Components of income tax expenses (benefit)    
Current income tax expense $ 1.5 $ 1.1
Deferred tax expense (benefit) 0.1 (5.7)
Total income tax expense (benefit), net $ 1.6 $ (4.6)
Reconciliation of income taxes    
Canadian enacted statutory rate (as a percent) 26.00% 26.00%
Computed income taxes at Canadian statutory rate $ 3.0 $ 5.2
Change in valuation allowance 2.8 2.9
Foreign exchange 2.5 1.8
Dividend withholding tax and other cash taxes 0.6  
Other permanent differences 0.2 2.7
Countries with different tax rates 1.1 2.4
Capital losses on tax restructuring 0.4  
Permanent differences 0.2 $ 2.7
Valuation allowance $ 178.1