Debt - Components of Debt (Details) - USD ($) $ in Millions	Sep. 30, 2018	Dec. 31, 2017
Debt Instrument [Line Items]
Debt payable—unconsolidated affiliate	$ 48.1	$ 42.4
Total debt	1,986.5	1,543.9
Debt payable within one year	22.8	20.1
Debt payable after one year	$ 1,963.7	$ 1,523.8
Weighted average interest rates on total debt	3.80%	4.70%
2025 Term Loan
Debt Instrument [Line Items]
Total debt	$ 940.7	$ 0.0
Unamortized discount and debt issuance costs	9.3	0.0
5.125% Senior Notes, Due 2021
Debt Instrument [Line Items]
Total debt	$ 695.4	$ 694.2
Interest rate (percent)	5.125%	5.125%
Unamortized discount and debt issuance costs	$ 4.6	$ 5.8
5.625% Senior Notes, Due 2024
Debt Instrument [Line Items]
Total debt	$ 296.9	$ 296.5
Interest rate (percent)	5.625%	5.625%
Unamortized discount and debt issuance costs	$ 3.1	$ 3.5
Term Loan B (USD)
Debt Instrument [Line Items]
Total debt	0.0	404.1
Unamortized discount and debt issuance costs	0.0	4.3
Term Loan B (EUR)
Debt Instrument [Line Items]
Total debt	0.0	94.0
Unamortized discount and debt issuance costs	0.0	1.0
Other borrowings
Debt Instrument [Line Items]
Total debt	$ 5.4	$ 12.7