Employee Benefit Plans - Funded Status (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Change in benefit obligation:
Benefit obligation at beginning of year	$ 121.0	$ 115.1
Service cost	2.4	2.2	$ 2.5
Interest cost	4.2	4.1	4.3
Participant contributions	1.0	0.9
Curtailments	0.0	0.2
Actuarial loss	1.2	17.2
Benefits paid	(6.0)	(3.0)
Settlement payments	0.0	(3.8)
Other, principally foreign exchange	10.0	(11.9)
Benefit obligation at end of year	133.8	121.0	115.1
Change in plan assets:
Fair value of plan assets at beginning of year	99.3	104.5
Actual gain on plan assets	10.4	4.8
Employer contributions	3.1	2.8
Participant contributions	1.0	0.9
Benefits paid	(6.0)	(3.0)
Other, principally foreign exchange	7.7	(10.7)
Fair value of assets at end of year	115.5	99.3	$ 104.5
Amounts recognized in the consolidated balance sheets:
Funded status (current)	0.0	0.0
Funded status (non-current)	(18.3)	(21.6)
Accumulated other comprehensive loss:
Unrecognized actuarial loss	20.6	28.3
Unrecognized prior service cost	0.5	(3.7)
Deferred taxes	(4.7)	(4.9)
Net amount recognized	$ (1.9)	$ (1.9)