v3.5.0.2
Income taxes (Details) - USD ($)
$ in Millions
3 Months Ended 9 Months Ended
Sep. 30, 2016
Sep. 30, 2015
Sep. 30, 2016
Sep. 30, 2015
Components of income tax expenses (benefit)        
Current income tax expense $ 0.8 $ (1.6) $ 2.6 $ 5.7
Deferred tax benefit 1.8 3.0 (16.8) (6.0)
Total income tax (benefit) expense, net $ 2.6 $ 1.4 $ (14.2) $ (0.3)
Reconciliation of income taxes        
Canadian enacted statutory rate (as a percent) 26.00% 26.00% 26.00% 26.00%
Computed income taxes at Canadian statutory rate $ 20.2 $ 0.5 $ 32.2 $ 0.3
Goodwill impairment 22.5   22.5  
Impairment of goodwill     78.8  
Capital loss on intercompany notes 7.2   3.0  
Foreign exchange   2.2 5.5 6.3
Change in valuation allowance 8.6 4.0 13.2 10.1
Dividend withholding tax and other cash taxes   2.6   1.0
Other permanent differences 0.8 0.1 1.1 0.6
Tax credit   3.6   3.6
Operating in higher tax rate jurisdictions 1.9   2.8 4.0
Valuation allowance 188.5   188.5  
Capital gain on repatriation of wind sale proceeds   $ 2.8   $ 2.8
United States        
Reconciliation of income taxes        
Change in valuation allowance (0.7)   (18.4)  
Canada        
Reconciliation of income taxes        
Change in valuation allowance 9.3   31.6  
Capital losses on tax restructuring $ 18.5   $ 18.5