Employee Benefits - Summary of Components of Net Periodic Postretirement Benefit Cost (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Defined Benefit Plan Disclosure [Line Items]
Total net periodic postretirement benefit cost	$ 1.4	$ 0.6
Pension Plans
Defined Benefit Plan Disclosure [Line Items]
Service cost	1.4
Interest cost	0.2
Expected return on plan assets	(0.2)
Total net periodic postretirement benefit cost	1.4
Other Postretirement Benefits Plan
Defined Benefit Plan Disclosure [Line Items]
Service cost	0.4
Interest cost	0.5
Total net periodic postretirement benefit cost	0.9
Postretirement Health Coverage | Salaried VEBA
Defined Benefit Plan Disclosure [Line Items]
Interest cost	0.5	0.4
Expected return on plan assets	(0.8)	(0.8)
Amortization of prior service cost	1.2	0.9
Amortization of net actuarial loss		0.1
Total net periodic postretirement benefit cost	$ 0.9	$ 0.6