v3.19.3.a.u2
Fair value of financial instruments - recurring (Details) - USD ($)
$ in Millions
Dec. 31, 2019
Dec. 31, 2018
Assets:    
Restricted cash $ 7.7 $ 2.1
Recurring    
Assets:    
Cash and cash equivalents 74.9 68.3
Restricted cash 7.7 2.1
Derivative instruments asset 0.7 4.5
Total 83.3 74.9
Liabilities:    
Derivative instruments liability 27.9 19.9
Total 27.9 19.9
Recurring | Level 1    
Assets:    
Cash and cash equivalents 74.9 68.3
Restricted cash 7.7 2.1
Total 82.6 70.4
Recurring | Level 2    
Assets:    
Derivative instruments asset 0.7 4.5
Total 0.7 4.5
Liabilities:    
Derivative instruments liability 24.7 18.7
Total 24.7 18.7
Recurring | Level 3    
Liabilities:    
Derivative instruments liability 3.2 1.2
Total $ 3.2 $ 1.2