Fair Value Accounting - Assets and liabilities measured at fair value on recurring basis (Details) - USD ($) $ in Millions		Jun. 30, 2019	Dec. 31, 2018
Liabilities:
Derivative liability		$ 4.6
Fair Value, Measurements, Recurring
Assets:
Cash equivalents		50.0	$ 30.0
Total assets		50.0	30.0
Liabilities:
Contingent consideration liability	[1]	5.2
Total liabilities		9.8	1.2
Fair Value, Measurements, Recurring | Interest Rate Swap
Liabilities:
Derivative liability	[2]	4.6	1.2
Fair Value, Inputs, Level 1 | Fair Value, Measurements, Recurring
Assets:
Cash equivalents		50.0	30.0
Total assets		50.0	30.0
Liabilities:
Contingent consideration liability	[1]	0.0
Total liabilities		0.0	0.0
Fair Value, Inputs, Level 1 | Fair Value, Measurements, Recurring | Interest Rate Swap
Liabilities:
Derivative liability	[2]	0.0	0.0
Fair Value, Inputs, Level 2 | Fair Value, Measurements, Recurring
Assets:
Cash equivalents		0.0	0.0
Total assets		0.0	0.0
Liabilities:
Contingent consideration liability	[1]	0.0
Total liabilities		4.6	1.2
Fair Value, Inputs, Level 2 | Fair Value, Measurements, Recurring | Interest Rate Swap
Liabilities:
Derivative liability	[2]	4.6	1.2
Fair Value, Inputs, Level 3 | Fair Value, Measurements, Recurring
Assets:
Cash equivalents		0.0	0.0
Total assets		0.0	0.0
Liabilities:
Contingent consideration liability	[1]	5.2
Total liabilities		5.2	0.0
Fair Value, Inputs, Level 3 | Fair Value, Measurements, Recurring | Interest Rate Swap
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 Sheets.