v2.4.0.8
Income taxes (Details) (USD $)
In Millions, unless otherwise specified
3 Months Ended 6 Months Ended
Jun. 30, 2013
Jun. 30, 2012
Jun. 30, 2013
Jun. 30, 2012
Income taxes        
Income tax benefit from continuing operations     $ 1.9  
Expected income tax expense     1.7  
Permanent differences benefits generated from U.S. treasury grant proceeds, production tax credits and foreign exchange differences     19.7  
Increase in the valuation allowance     12.7  
Dividend withholding and preferred share taxes     2.6  
Other permanent differences     0.8  
Canadian enacted statutory rate (as a percent)     25.00%  
Components of income tax expenses (benefit)        
Current income tax expense 3.4 3.0 5.4 3.8
Deferred tax benefit (2.8) (8.3) (7.3) (26.0)
Total income tax expense (benefit) 0.6 (5.3) (1.9) (22.2)
Deferred tax assets:        
Valuations allowance $ (127.1)   $ (127.1)