Summary of Significant Accounting Policies - Components of Accumulated Other Comprehensive Income (Details) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated other comprehensive loss	$ 597.7	$ 557.9	$ 546.7	$ 508.3
Accumulated pension and OPEB liability adjustments
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated other comprehensive loss	(24.3)	(28.2)
Accumulated other comprehensive loss, Income tax benefit	12.8	11.4
Accumulated unrealized loss on derivative instruments
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated other comprehensive loss	(3.5)	(0.6)
Accumulated other comprehensive loss, Income tax benefit	1.6	1.6
Accumulated unrealized foreign currency translation adjustments
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated other comprehensive loss	(94.8)	(95.7)
Accumulated other comprehensive loss, Income tax benefit	5.0	1.7
Accumulated other comprehensive loss
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated other comprehensive loss	$ (122.6)	$ (124.5)	$ (89.4)	$ (139.3)