v3.20.1
Fair value of financial instruments - recurring (Details) - Recurring - USD ($)
$ in Millions
Mar. 31, 2020
Dec. 31, 2019
Assets:    
Cash and cash equivalents $ 47.8 $ 74.9
Restricted cash 0.5 7.7
Derivative instruments asset   0.7
Total 48.3 83.3
Liabilities:    
Derivative instruments liability 34.5 27.9
Total 34.5 27.9
Level 1    
Assets:    
Cash and cash equivalents 47.8 74.9
Restricted cash 0.5 7.7
Total 48.3 82.6
Level 2    
Assets:    
Derivative instruments asset   0.7
Total   0.7
Liabilities:    
Derivative instruments liability 28.9 24.7
Total 28.9 24.7
Level 3    
Liabilities:    
Derivative instruments liability 5.6 3.2
Total $ 5.6 $ 3.2