v2.4.0.8
Basis of presentation and summary of significant accounting policies (Details 2) (USD $)
In Millions, unless otherwise specified
 3 Months Ended 9 Months Ended
Sep. 30, 2013
Sep. 30, 2012
Sep. 30, 2013
Sep. 30, 2012
Changes in accumulated other comprehensive loss by component        
Balance at beginning of period     $ 9.4  
Other comprehensive income (loss):        
Foreign currency translation adjustments 10.7 19.3 (19.3) 22.6
Tax expense   3.1 (1.9) (19.1)
Total Other comprehensive income (loss) 10.8 19.1 (18.2) 22.3
Balance at end of period (8.7)   (8.7)  
Foreign currency translation
        
Changes in accumulated other comprehensive loss by component        
Balance at beginning of period (17.4) (0.1) 12.7 (3.4)
Other comprehensive income (loss):        
Foreign currency translation adjustments 10.7 19.3 (19.3) 22.6
Balance at end of period (6.7) 19.2 (6.7) 19.2
Cash flow hedges
        
Changes in accumulated other comprehensive loss by component        
Balance at beginning of period (0.4) (1.5) (1.4) (1.4)
Other comprehensive income (loss):        
Net change from periodic revaluations (0.2) (0.5) 0.9 (1.4)
Tax benefit 0.1 0.2 (0.4) 0.6
Total Other comprehensive loss before reclassifications, net of tax (0.1) (0.3) 0.5 (0.8)
Tax expense (0.1)   (0.4) (0.3)
Total amount reclassified from Accumulated other comprehensive loss, net of tax 0.2 0.1 0.6 0.5
Total Other comprehensive income (loss) 0.1 (0.2) 1.1 (0.3)
Balance at end of period (0.3) (1.7) (0.3) (1.7)
Cash flow hedges | Amount reclassified from accumulated other comprehensive income
        
Other comprehensive income (loss):        
Net amount reclassified to earnings: 0.3 0.1 1.0 0.8
Cash flow hedges | Amount reclassified from accumulated other comprehensive income | Interest rate swaps
        
Other comprehensive income (loss):        
Net amount reclassified to earnings: 0.3 0.4 1.2 1.2
Cash flow hedges | Amount reclassified from accumulated other comprehensive income | Fuel commodity swaps
        
Other comprehensive income (loss):        
Net amount reclassified to earnings:   $ (0.3) $ (0.2) $ (0.4)