Employee Benefits - Schedule of Reconciliation of Projected Benefit Obligation and Fair Value of Plan Assets (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Benefit obligation at beginning of year	$ 1,128.8	$ 1,073.2
Interest cost	37.1	45.7
Benefits paid	(102.1)	(96.7)
Actuarial (gain) loss	78.5	106.5
Other		0.1
Benefit obligation at year end	1,142.3	1,128.8
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets at prior year end	900.0	874.9
Actual return on plan assets	356.3	112.1
Employer contributions	36.5	9.7
Benefits paid	(102.1)	(96.7)
Fair value of plan assets at year end	1,190.7	900.0
Funded status at year end	$ 48.4	$ (228.8)