Postretirement Benefit Plans (Details) - Postretirement Plan - USD ($) $ in Millions	1 Months Ended	3 Months Ended
	Jan. 31, 2021	Mar. 31, 2021	Mar. 31, 2020
Defined Benefit Plan Disclosure [Line Items]
Interest cost		$ 0.4	$ 0.5
Expected return on plan assets		0.0	(0.1)
Amortization of prior service credit		(2.5)	(2.4)
Net periodic benefit credit		$ (2.1)	$ (2.0)
Net periodic benefit cost	$ 11.1