Employee Benefits - Schedule of net periodic benefit costs (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Retirement Benefits [Abstract]
Service and other cost	$ (0.3)	$ 0.0	$ (2.6)
Interest cost	(5.2)	(5.1)	(7.2)
Expected return on assets	7.9	8.4	8.9
Curtailments, settlements and terminations	0.0	0.0	9.6
Amortization of net loss	(0.1)	(0.1)	(0.3)
Net periodic pension benefit	$ 2.3	$ 3.2	$ 8.4