Components of Net Periodic Pension Cost (Details) - USD ($) $ in Millions	3 Months Ended	9 Months Ended	12 Months Ended
	Apr. 01, 2017	Dec. 31, 2017	Dec. 31, 2019	Dec. 31, 2018
Components of net periodic pension costs
Net periodic pension (benefit) cost	$ (14.4)	$ (21.9)	$ (19.4)	$ (18.1)
Pension Plans, Defined Benefit
Components of net periodic pension costs
Service cost for benefits earned	0.6	1.6	2.0	2.3
Interest cost on projected benefit obligation	9.7	28.0	33.5	31.4
Expected return on plan assets	(11.0)	(33.5)	(31.4)	(42.8)
Amortization of prior service cost	0.1	0.0	0.0	0.0
Amortization of net actuarial losses	6.3	0.0	0.0	0.0
Settlement charge	0.0	2.1	0.0	0.0
Net actuarial (gain) loss	0.0	(23.5)	(16.6)	4.2
Net periodic pension (benefit) cost	$ 5.7	$ (25.3)	$ (12.5)	$ (4.9)