Employee Benefit Plans - Net Periodic Benefit Cost (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Retirement Benefits [Abstract]
Service cost	$ 2.5	$ 2.4	$ 2.2
Interest cost	3.8	4.2	4.1
Expected return on plan assets	(5.4)	(5.9)	(5.8)
Amortization of actuarial losses	1.0	1.4	0.3
Net periodic cost	$ 1.9	$ 2.1	$ 0.8