v2.4.0.8
Guarantees and condensed consolidating financial information (Details 4) (USD $)
In Millions, unless otherwise specified
 3 Months Ended 9 Months Ended
Sep. 30, 2013
Sep. 30, 2012
Sep. 30, 2013
Sep. 30, 2012
Condensed consolidating statement of operations and comprehensive income        
Net income (loss) $ (40.6) $ (4.5) $ (31.7) $ (45.8)
Other comprehensive income (loss):        
Unrealized gain on hedging activities (0.1) (0.3) 0.5 (0.8)
Net amount reclassified to earnings 0.2 0.1 0.6 0.5
Net unrealized gain (loss) on derivatives 0.1 (0.2) 1.1 (0.3)
Foreign currency translation adjustments 10.7 19.3 (19.3) 22.6
Other comprehensive income (loss), net of tax 10.8 19.1 (18.2) 22.3
Comprehensive income (loss) (29.8) 14.6 (49.9) (23.5)
Less: Comprehensive income attributable to noncontrolling interest 0.7 3.0 6.2 9.1
Comprehensive income (loss) attributable to Atlantic Power Corporation (30.5) 11.6 (56.1) (32.6)
Eliminations
        
Condensed consolidating statement of operations and comprehensive income        
Net income (loss) (0.1)   (0.1)  
Other comprehensive income (loss):        
Comprehensive income (loss) (0.1)   (0.1)  
Comprehensive income (loss) attributable to Atlantic Power Corporation (0.1)   (0.1)  
Guarantor Subsidiaries | Reportable legal entities
        
Condensed consolidating statement of operations and comprehensive income        
Net income (loss) (23.4)   (11.0)  
Other comprehensive income (loss):        
Unrealized gain on hedging activities (0.1)   0.5  
Net amount reclassified to earnings 0.2   0.6  
Net unrealized gain (loss) on derivatives 0.1   1.1  
Foreign currency translation adjustments 10.7   (19.3)  
Other comprehensive income (loss), net of tax 10.8   (18.2)  
Comprehensive income (loss) (12.6)   (29.2)  
Less: Comprehensive income attributable to noncontrolling interest 0.7   6.2  
Comprehensive income (loss) attributable to Atlantic Power Corporation (13.3)   (35.4)  
Curtis Palmer | Reportable legal entities
        
Condensed consolidating statement of operations and comprehensive income        
Net income (loss)     5.4  
Other comprehensive income (loss):        
Comprehensive income (loss)     5.4  
Comprehensive income (loss) attributable to Atlantic Power Corporation     5.4  
Atlantic Power | Reportable legal entities
        
Condensed consolidating statement of operations and comprehensive income        
Net income (loss) (17.1)   (26.0)  
Other comprehensive income (loss):        
Comprehensive income (loss) (17.1)   (26.0)  
Comprehensive income (loss) attributable to Atlantic Power Corporation $ (17.1)   $ (26.0)