v3.4.0.3
Accounting for derivative instruments - AOCI (Details) - USD ($)
$ in Millions
3 Months Ended
Mar. 31, 2016
Mar. 31, 2015
AOCI Attributable to Parent, Net of Tax    
Change in fair value of cash flow hedges $ (0.5) $ (0.5)
Realized from OCI during the period 0.2 0.2
Interest rate swaps    
AOCI Attributable to Parent, Net of Tax    
Accumulated OCI balance at beginning of period 0.0 0.1
Change in fair value of cash flow hedges (0.5) (0.5)
Realized from OCI during the period 0.2 0.2
Accumulated OCI balance at end of period $ (0.3) $ (0.2)