Restructuring Charge - Restructuring Reserve and Utilization (Details) - USD ($) $ in Millions	1 Months Ended	12 Months Ended
	Feb. 07, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Restructuring Reserve [Rollforward]
Balance at beginning of period	$ 7.6	$ 11.1	$ 7.6	$ 16.2
Impact of purchase accounting			3.2
Charge taken during the period	0.1	15.8	48.8	25.4
Payments made during period	(2.1)	(17.0)	(39.1)	(33.8)
Payments and other adjustments made during period			(40.9)	(34.0)
Reclassification related to leases pursuant to the adoption of Topic 842	(2.4)
Balance at end of period	3.2	9.9	11.1	7.6
Employee Severance [Member]
Restructuring Reserve [Rollforward]
Balance at beginning of period	4.7	6.3	4.7	12.7
Impact of purchase accounting			3.2
Charge taken during the period	0.1	9.9	36.6	22.3
Payments made during period	(1.6)	(13.7)
Payments and other adjustments made during period			(33.5)	(30.3)
Reclassification related to leases pursuant to the adoption of Topic 842	0.0
Balance at end of period	3.2	2.5	6.3	4.7
Contract Termination and Other Restructuring [Member]
Restructuring Reserve [Rollforward]
Balance at beginning of period	2.9	4.8	2.9	3.5
Impact of purchase accounting			0.0
Charge taken during the period	0.0	5.9	12.2	3.1
Payments made during period	(0.5)	(3.3)
Payments and other adjustments made during period			(7.4)	(3.7)
Reclassification related to leases pursuant to the adoption of Topic 842	(2.4)
Balance at end of period	$ 0.0	$ 7.4	$ 4.8	$ 2.9