Employee Benefit Plans - Changes in Projected Benefit Obligations and Plan Assets (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Changes in projected benefit obligations:
Projected benefit obligations at beginning of period	$ 46.5	$ 42.2
Projected benefit obligations assumed in business combination			$ 49.8
Service cost	1.0	0.9	0.9
Interest cost	0.9	1.0	0.7
Actuarial loss (gain)	(1.3)	5.0	(7.2)
Benefits paid	(1.0)	(1.0)	(0.8)
Currency translation and other	6.6	(1.6)	(1.2)
Projected benefit obligations at end of period	52.7	46.5	42.2
Changes in plan assets:
Fair value of plan assets at beginning of period	4.5	4.2
Fair value of plan assets acquired in business combination			3.8
Employer contributions	0.6	0.5	0.5
Actual return on plan assets		0.1	0.1
Currency translation and other	0.7	(0.3)	(0.2)
Fair value of plan assets at end of period	5.8	4.5	4.2
Accrued pension benefits	$ 46.9	$ 42.0	$ 38.0