Fair Value Accounting - Assets and liabilities measured at fair value on recurring basis (Details) - Fair value measurements, recurring - USD ($) $ in Millions		Dec. 31, 2019	Dec. 31, 2018
Assets:
Cash equivalents		$ 155.3	$ 30.0
Total assets		155.3	30.0
Liabilities:
Contingent consideration liability	[1]	6.4
Total liabilities		10.7	1.2
Interest rate hedges
Liabilities:
Derivative liability	[2]	4.3	1.2
Level 1
Assets:
Cash equivalents		155.3	30.0
Total assets		155.3	30.0
Liabilities:
Contingent consideration liability	[1]	0.0
Total liabilities		0.0	0.0
Level 1 | Interest rate hedges
Liabilities:
Derivative liability	[2]	0.0	0.0
Level 2
Assets:
Cash equivalents		0.0	0.0
Total assets		0.0	0.0
Liabilities:
Contingent consideration liability	[1]	0.0
Total liabilities		4.3	1.2
Level 2 | Interest rate hedges
Liabilities:
Derivative liability	[2]	4.3	1.2
Level 3
Assets:
Cash equivalents		0.0	0.0
Total assets		0.0	0.0
Liabilities:
Contingent consideration liability	[1]	6.4
Total liabilities		6.4	0.0
Level 3 | Interest rate hedges
Liabilities:
Derivative liability	[2]	$ 0.0	$ 0.0

[1] Current portion included in accrued liabilities and non-current portion included in other liabilities on the Consolidated Balance Sheets.

[2] Included in other liabilities on the Consolidated Balance Sheet.