Restructuring - Rollforward of all restructuring accrual (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Rollforward of all restructuring accrual
Balance at beginning of period	$ 2.0	$ 3.3
Restructuring expense	1.5	4.5
Use of reserve	(1.1)	(3.0)
Reserve reclassification		(0.2)
Balance at end of period	$ 2.4	$ 4.6