Employee Benefit Plans - Projected Benefit Obligation and Plan Asset Fund Status (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Change in projected benefit obligation:
Projected benefit obligation at beginning of year	$ 58.5	$ 53.6
Interest cost	1.8	2.2	$ 2.1
Assumption changes	5.2	5.4
Benefits paid	(2.7)	(2.5)
Actuarial gains	(0.3)	(0.2)
Projected benefit obligation at year end	62.5	58.5	53.6
Change in plan assets:
Fair value of plan assets at beginning of year	49.1	42.8
Actual return	6.4	8.4
Employer contributions	1.1	0.4
Benefits paid	(2.7)	(2.5)
Fair value of plan assets at year end	53.9	49.1	$ 42.8
Funded status (Accrued pension liabilities)	(8.6)	(9.4)
Unrecognized actuarial loss recognized in accumulated other comprehensive income (loss)	$ 14.9	$ 14.2