Accumulated Other Comprehensive Income (Loss) - Summary (Details) - USD ($) $ in Millions	1 Months Ended	12 Months Ended
	Feb. 07, 2019	Dec. 31, 2020	Dec. 31, 2019
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Balance at beginning of period	$ (13.5)	$ 1,577.7	$ (13.5)
Other comprehensive income (loss) before reclassifications	68.2	(84.3)	(24.0)
Amounts reclassified from accumulated other comprehensive loss, net of tax	2.8	1.8	0.5
Balance at end of period	(681.9)	3,577.7	1,577.7
Total
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Balance at beginning of period	(1,054.1)	(23.5)	(1,054.1)
Balance at end of period	(983.1)	(106.0)	(23.5)
Foreign Currency Translation Adjustments
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Balance at beginning of period	(235.5)	(6.6)	(235.5)
Other comprehensive income (loss) before reclassifications	5.7	23.3	(6.6)
Amounts reclassified from accumulated other comprehensive loss, net of tax	0.0	0.0	0.0
Balance at end of period	(229.8)	16.7	(6.6)
Defined Benefit Pension Plans
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Balance at beginning of period	(818.3)	(15.8)	(818.3)
Other comprehensive income (loss) before reclassifications	62.6	(106.2)	(15.8)
Amounts reclassified from accumulated other comprehensive loss, net of tax	2.8	(0.3)	0.0
Balance at end of period	(752.9)	(122.3)	(15.8)
Derivative Financial Instruments
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Balance at beginning of period	(0.3)	(1.1)	(0.3)
Other comprehensive income (loss) before reclassifications	(0.1)	(1.4)	(1.6)
Amounts reclassified from accumulated other comprehensive loss, net of tax	0.0	2.1	0.5
Balance at end of period	$ (0.4)	$ (0.4)	$ (1.1)